2-amino-3,5-difluoro-3,6-dimethyl-6-phenyl-3,4,5,6-tetrahydropyridines as BACE1 inhibitors for treating alzheimer&#39;s disease

ABSTRACT

The present invention is directed to compounds according to Formula (I) which compounds are inhibitors of the BACE1 enzyme. Separate aspects of the invention are directed to pharmaceutical compositions comprising said compounds and uses of the compounds to treat disorders for 5 which the reduction of Aβ deposits is beneficial such as Alzheimer&#39;s disease.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a § 371 National Stage Application ofPCT/EP2015/076014 (filed on Nov. 9, 2015; pending), which applicationclaims benefit of DK Patent Application No. PA 2015 00450, filed on Aug.7, 2015, and DK Patent Application No. PA 2014 00649, filed on Nov. 10,2014, each of which applications is hereby incorporated by reference inits entirety.

FIELD OF THE INVENTION

The present invention provides compounds which act as BACE1 inhibitors.Separate aspects of the invention are directed to pharmaceuticalcompositions comprising said compounds and uses of the compounds totreat neurodegenerative and cognitive disorders.

BACKGROUND ART

Dementia is a clinical syndrome characterized by deficits in multipleareas of cognition that cannot be explained by normal aging, anoticeable decline in function, and an absence of delirium. In addition,neuropsychiatric symptoms and focal neurological findings are usuallypresent. Dementia is further classified based on etiology. Alzheimer'sdisease (AD) is the most common cause of dementia, followed by mixed ADand vascular dementia, Lewy body dementia (DLB), and fronto-temporaldementia. β-Amyloid deposits and neurofibrillary tangles are consideredto be major pathologic characterizations associated with AD which ischaracterized by the loss of memory, cognition, reasoning, judgment, andorientation. Also affected, as the disease progresses, are motor,sensory and linguistic abilities until global impairment of multiplecognitive functions occurs. β-Amyloid deposits are predominantly anaggregate of Aβ peptide, which in turn is a product of the proteolysisof amyloid precursor protein (APP) as part of the β-amyloidogenicpathway. Aβ peptide results from the cleavage of APP at the C-terminalby one or more γ-secretases and at the N-terminal by β-secretase 1(BACE1) also known as aspartyl protease 2. BACE1 activity is correlateddirectly to the generation of Aβ peptide from APP.

Studies indicate that the inhibition of BACE1 impedes the production ofAβ peptide. Further, BACE1 co-localizes with its substrate APP in Golgiand endocytic compartments (Willem M, et al. Semin. Cell Dev. Biol,2009, 20, 175-182). Knock-out studies in mice have demonstrated theabsence of amyloid peptide formation while the animals are healthy andfertile (Ohno M, et al. Neurobiol. Dis., 2007, 26, 134-145). Geneticablation of BACE1 in APP-overexpressing mice has demonstrated absence ofplaque formation, and the reverse of cognitive deficits (Ohno M, et al.Neuron; 2004, 41, 27-33). BACE1 levels are elevated in the brains ofsporadic AD patients (Hampel and Shen, Scand. J. Clin. Lab. Invest.2009, 69, 8-12).

These convergent findings indicate that the inhibition of BACE1 may be atherapeutic target for the treatment of AD as well as disorders forwhich the reduction of Aβ deposits is beneficial.

AstraZeneca announced the discovery of AZD3839, a potent BACE1 inhibitorclinical candidate for the treatment of AD (Jeppsson, F., et al. J.Biol. Chem., 2012, 287, 41245-41257) in October 2012. The effort whichled to the discovery of AZD3839 was further described in Ginman, T., etal. J. Med. Chem., 2013, 56, 4181-4205. The Ginman publication describesthe issues which were overcome in connection with the discovery andidentification of AZD3839. These issues related to poor blood brainbarrier penetration and P-glycoprotein mediated efflux of the compoundsresulting in lack of brain exposure.

The Ginman manuscript hypothesized that the differences in brainexposure would largely be due to the core structures and StructureActivity Relationship data was provided wherein the in vitro propertieson the reported compounds were given into four tables according to coresub-types. In table 4, a series of amidine containing compounds aredescribed that were considered interesting from an activity perspective.However, the data suggests that the amidine containing core did notexhibit a favourable blood brain barrier permeability profile.

Researchers from Hoffmann-La Roche and Siena Biotech also reported thediscovery of amidine containing compounds (Woltering, T. J., et al.Bioorg. Med. Chem. Lett. 2013, 23, 4239-4243). These compounds(compounds 17 and 18 in the paper) were found not to have any in vivoeffect (lack of Aβ40 reduction in brain in wild type mice).

Contrary to the teachings of Ginman, et al. and Woltering, T. J., etal., the inventors have discovered a series of amidine compounds whichare brain penetrant. Accordingly, the present invention relates to novelcompounds having BACE1 inhibitory activity, to their preparation, totheir medical use and to medicaments comprising them.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide compounds thatinhibit BACE1. Accordingly, the present invention relates to compoundsof Formula I

wherein Ar is selected from the group consisting of phenyl, pyridyl,pyrimidyl, pyrazinyl, imidazolyl, pyrazolyl, thiazolyl, oxazolyl,isoxazolyl, and where the Ar is optionally substituted with one or moresubstituent selected from halogen, CN, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆alkynyl, C₁-C₆ fluoroalkyl or C₁-C₆ alkoxy; andR¹ is one or more hydrogen, halogen, C₁-C₃ fluoroalkyl or C₁-C₃ alkyl;or a pharmaceutically acceptable salt thereof.

In one embodiment the present invention provides a compound of Formula Ior a pharmaceutically acceptable salt thereof for use in therapy.

The present invention further provides a pharmaceutical compositioncomprising a compound of Formula I or a pharmaceutically acceptable saltthereof and a pharmaceutically acceptable carrier.

In one embodiment the invention provides the use of a compound ofFormula I or a pharmaceutically acceptable salt thereof in themanufacture of a medicament for the treatment of a neurodegenerative orcognitive disorder.

In one embodiment, the invention provides a compound of Formula I or apharmaceutically acceptable salt thereof for use in a method for thetreatment of a neurodegenerative or cognitive disorder.

In one embodiment the present invention provides a method of treating aneurodegenerative or cognitive disorder comprising administering atherapeutically effective amount of a compound of Formula I or apharmaceutically acceptable salt thereof to a patient in need thereof.

Further embodiments of the invention are provided immediately below:

In one embodiment, the compound of the present invention is of formulaIa or Ib

or a pharmaceutically acceptable salt thereof.

In one embodiment, R¹ is F or H, particularly F.

In one embodiment, the compound of the present invention is of FormulaIa and R¹ is F.

In one embodiment, Ar is optionally substituted with one or moresubstituents selected from F, Cl, Br, CN, C₁-C₃ alkyl, C₁-C₃ fluoroalkylor C₁-C₃ alkoxy.

In one embodiment, Ar is optionally substituted phenyl.

In one embodiment, Ar is optionally substituted pyridyl.

In one embodiment, Ar is optionally substituted pyrimidyl.

In one embodiment, Ar is optionally substituted pyrazinyl.

In one embodiment, Ar is optionally substituted imidazolyl.

In one embodiment, Ar is optionally substituted pyrazolyl.

In one embodiment, Ar is optionally substituted thiazolyl.

In one embodiment, Ar is optionally substituted oxazolyl.

In one embodiment, Ar is optionally substituted isoxazolyl.

In one embodiment, the compound is selected from the group consistingof:

-   N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-fluoropicolinamide,-   N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypyrazine-2-carboxamide,-   N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypicolinamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-fluoropicolinamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypyrazine-2-carboxamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-2-methyloxazole-4-carboxamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypicolinamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)picolinamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-chloropicolinamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-1-methyl-1H-imidazole-2-carboxamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(trifluoromethyl)pyrazine-2-carboxamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-4-methylthiazole-2-carboxamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-2-(difluoromethyl)oxazole-4-carboxamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-1-(difluoromethyl)-1H-pyrazole-3-carboxamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(difluoromethyl)pyrazine-2-carboxamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-4-chlorobenzamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-di-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-cyanopicolinamide,-   N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,45-tetrahydropyridin-2-yl)-4,5-difluorophenyl)-5-(methoxy-d₃)picolinamide,-   N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)picolinamide,-   N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)pyrazine-2-carboxamide,-   N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-cyano-3-methylpicolinamide,-   N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4,5-difluorophenyl)-5-(methoxy-d₃)picolinamide,-   N-(3-((2R,3R,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)picolinamide,-   N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-bromopicolinamide    or a pharmaceutically acceptable salt thereof.

A separate embodiment is directed to a pharmaceutical compositioncomprising a compound from the above list and a pharmaceuticallyacceptable carrier.

Another embodiment is directed to a method of treating aneurodegenerative or cognitive disorder comprising administering atherapeutically effective amount of a compound from the above list topatient in need thereof.

Yet another embodiment is directed to a use of a compound from the abovelist for the manufacture of a medicament for treating aneurodegenerative or cognitive disorder.

In one embodiment the invention provides a compound from the above listfor use in therapy.

Yet another embodiment of the invention is directed to a compound fromthe above list for use in the treatment of a neurodegenerative orcognitive disorder.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1: X-ray structure of5-bromo-N-(3-((2R,3S,5S)-3,5-difluoro-2,5-dimethyl-6-thioxopiperidin-2-yl)-4-fluorophenyl)picolinamide.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is based on the discovery that the compounds ofFormula I are inhibitors of BACE1, and as such, are useful for thetreatment of related disorders. Certain aspects of the invention areexplained in greater detail below but this description is not intendedto be a detailed catalog of all the different ways in which theinvention may be implemented, or all the features that may be added tothe instant invention. Hence, the following specification is intended toillustrate some embodiments of the invention, and not to exhaustivelyspecify all permutations, combinations and variations thereof.

As used herein, the term “C₁-C₆ alkyl” refers to a straight chained orbranched saturated hydrocarbon having from one to six carbon atomsinclusive. Examples of C₁-C₆ alkyl include, but are not limited to,methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl, 2-methyl-2-propyl,2-methyl-1-propyl, n-pentyl and n-hexyl. Similarly, the term “C₁-C₃alkyl” refers to a straight chained or branched saturated hydrocarbonhaving from one to three carbon atoms inclusive. Examples of C₁-C₃include, but are not limited to, methyl, ethyl and n-propyl.

Likewise, the term “C₁-C₆ alkoxy” refers to a straight chained orbranched saturated alkoxy group having from one to six carbon atomsinclusive with the open valency on the oxygen. Examples of C₁-C₆ alkoxyinclude, but are not limited to, methoxy, ethoxy, n-butoxy, t-butoxy andn-hexyloxy. The “C₁-C₆ alkoxy” is optionally substituted with one ormore fluorine atoms.

As used herein, the term “C₁-C₆ fluoroalkyl” refers to a straightchained or branched saturated hydrocarbon having from one to six carbonatoms inclusive substituted with one or more fluorine atoms. Examples ofC₁-C₆ fluoroalkyl include, but are not limited to, trifluoromethyl,pentafluoroethyl, 1-fluoroethyl, monofluoromethyl, difluoromethyl,1,2-difluoroethyl and 3,4 difluorohexyl. Similarly, the term “C₁-C₃fluoroalkyl” refers to a straight chained or branched saturatedhydrocarbon having from one to three carbon atoms inclusive substitutedwith one or more fluorine atoms per carbon atom.

The term “halogen” refers to fluorine, chlorine, bromine and iodine.

The term “C₂-C₆ alkenyl” refers to a branched or unbranched alkenylgroup having from two to six carbon atoms and one double bond, includingbut not limited to ethenyl, propenyl, and butenyl.

The term “C₂-C₆ alkynyl” shall mean a branched or unbranched alkynylgroup having from two to six carbon atoms and one triple bond, includingbut not limited to ethynyl, propynyl and butynyl.

As used herein, the phrase “effective amount” when applied to a compoundof the invention, is intended to denote an amount sufficient to cause anintended biological effect. The phrase “therapeutically effectiveamount” when applied to a compound of the invention is intended todenote an amount of the compound that is sufficient to ameliorate,palliate, stabilize, reverse, slow or delay the progression of adisorder or disease state, or of a symptom of the disorder or disease.In an embodiment, the method of the present invention provides foradministration of combinations of compounds. In such instances, the“effective amount” is the amount of the compound in said combinationsufficient to cause the intended biological effect.

The term “treatment” or “treating” as used herein means ameliorating orreversing the progress or severity of a disease or disorder, orameliorating or reversing one or more symptoms or side effects of suchdisease or disorder. “Treatment” or “treating”, as used herein, alsomeans to inhibit or block, as in retard, arrest, restrain, impede orobstruct, the progress of a system, condition or state of a disease ordisorder. For purposes of this invention, “treatment” or “treating”further means an approach for obtaining beneficial or desired clinicalresults, where “beneficial or desired clinical results” include, withoutlimitation, alleviation of a symptom, diminishment of the extent of adisorder or disease, stabilized (i.e., not worsening) disease ordisorder state, delay or slowing of a disease or disorder state,amelioration or palliation of a disease or disorder state, and remissionof a disease or disorder, whether partial or total.

The present invention is based on the discovery that compounds ofFormula I are inhibitors of BACE1, and as such, are useful for thetreatment of disorders which pathological characteristics compriseβ-amyloid deposits and neurofibrillary tangles, such asneurodegenerative or cognitive disorders.

The compounds of the present invention are, as discussed above, expectedto be useful in the treatment of Alzheimer's disease due to theireffects on β-amyloid deposits and neurofibrillary tangles. This includesfamilial Alzheimer's disease where patients carry mutations on specificgenes intimately involved in the production of Aβ peptide. It is,however, important to note that aggregates of Aβ peptide is not limitedto familial Alzheimer's disease but is similarly an importantpathophysiological characteristics of the more common sporadicAlzheimer's disease [Mol Cell Neurosci, 66, 3-11, 2015].

The compounds of the present invention are also believed to be useful inthe treatment of early-stage Alzheimer's disease, i.e. disease stageswhere the biological and structural changes have started but theclinical manifestations of the disease have not yet become evident orare not yet well developed. Early-stage Alzheimer's disease may, infact, start years before any clinical sign of the disease becomesmanifest. Early-stage Alzheimer's disease includes prodromal Alzheimer'sdisease, preclinical Alzheimer's disease and mild cognitive impairment.Although mild cognitive impairment may be unrelated to Alzheimer'sdisease it is often a transitional stage to Alzheimer's disease or dueto Alzheimer's disease. Preclinical and prodromal Alzheimer's diseaseare asymptomatic stages, and they are typically diagnosed by thepresence of Alzheimer's disease related biomarkers. In this context thecompounds of the present invention are believed to be useful in slowingdown the progression of early-stage Alzheimer's disease, such as mildcognitive impairment to Alzheimer's disease. The compounds of thepresent invention are also believed to be useful in the treatment ofmemory loss, attention deficits and dementia associated with Alzheimer'sdisease.

Other diseases, in addition to the continuum of Alzheimer's disease, arecharacterized by β-amyloid deposits and neurofibrillary tangles. Thisincludes e.g. Trisomy 21 also known as Down's syndrome. Patientssuffering from Down's syndrome have an extra chromosome 21 whichchromosome contains the gene for the amyloid precursor protein (APP).The extra chromosome 21 leads to overexpression of APP, which leads toincreased levels of Aβ peptide, which eventually causes the markedlyincreased risk of developing Alzheimer's disease seen in Down's syndromepatients [Alzheimer's & Dementia, 11, 700-709, 201]. Cerebral amyloidangiopathy is also characterized by β-amyloid deposits andneurofibrillary tangles in blood vessels of the central nervous system[Pharmacol Reports, 67, 195-203, 2015] and is as such expected to betreatable with compounds of the present invention.

In one embodiment, the present invention provides a method of treating adisease selected from Alzheimer's disease (familial or sporadic),preclinical Alzheimer's disease, prodromal Alzheimer's disease, mildcognitive impairment, Down's syndrome and cerebral amyloid angiopathy,the method comprising the administration of a therapeutically effectiveamount of a compound of Formula I or a pharmaceutically acceptable saltthereof to a patient in need thereof.

The present invention further provides a method of inhibiting BACE1 in apatient comprising administering to a patient in need thereof atherapeutically effective amount of a compound of Formula I or apharmaceutically acceptable salt thereof.

The present invention also provides a method of inhibiting β-secretasemediated cleavage of amyloid precursor protein comprising administeringto a patient in need of such treatment a therapeutically effectiveamount a compound of Formula I or a pharmaceutically acceptable saltthereof.

In further embodiments, the present invention provides the use of acompound of Formula I or a pharmaceutically acceptable salt thereof forthe manufacture of a medicament for the treatment of disease selectedfrom Alzheimer's disease (familial or sporadic), preclinical Alzheimer'sdisease, prodromal Alzheimer's disease, mild cognitive impairment,Down's syndrome or cerebral amyloid angiopathy.

The present invention also provides the use of a compound of Formula Ior a pharmaceutically acceptable salt thereof for the manufacture of amedicament for the inhibition of BACE1. The present invention furtherprovides the use of a compound of Formula I or a pharmaceuticallyacceptable salt thereof for the manufacture of a medicament for theinhibition of production or accumulation of Aβ peptide.

In one embodiment, the present invention provides a compound of FormulaI or a pharmaceutically acceptable salt thereof for use in a method forthe treatment of a disease selected form Alzheimer's disease (familialor sporadic), preclinical Alzheimer's disease, prodromal Alzheimer'sdisease, mild cognitive impairment, Down's syndrome or cerebral amyloidangiopathy.

In one embodiment, the present invention relates to a compound ofFormula I or a pharmaceutically acceptable salt thereof for use in amethod for inhibiting of BACE1 or in a method for inhibiting ofproduction or accumulation of Aβ peptide.

In a further embodiment, the invention provides a pharmaceuticalformulation adapted for any of the above treatments and uses.

In one embodiment, a mammal is a human.

In one embodiment, the patient is a human patient.

The present invention also comprises salts of the present compounds,typically, pharmaceutically acceptable salts. Such salts includepharmaceutically acceptable acid addition salts. Acid addition saltsinclude salts of inorganic acids as well as organic acids.

Representative examples of suitable inorganic acids includehydrochloric, hydrobromic, hydroiodic, phosphoric, sulfuric, sulfamic,nitric acids and the like. Representative examples of suitable organicacids include formic, acetic, trichloroacetic, trifluoroacetic,propionic, benzoic, cinnamic, citric, fumaric, glycolic, itaconic,lactic, methanesulfonic, maleic, malic, malonic, mandelic, oxalic,picric, pyruvic, salicylic, succinic, methane sulfonic, ethanesulfonic,tartaric, ascorbic, pamoic, bismethylene salicylic, ethanedisulfonic,gluconic, citraconic, aspartic, stearic, palmitic,ethylenediaminetetraacetic acid (EDTA), glycolic, p-aminobenzoic,glutamic, benzenesulfonic, p-toluenesulfonic acids, theophylline aceticacids, as well as the 8-halotheophyllines (for example,8-bromotheophylline and the like). Further examples of pharmaceuticallyacceptable inorganic or organic acid addition salts include thepharmaceutically acceptable salts listed in S. M. Berge, et al., J.Pharm. Sci., 1977, 66, 2.

Furthermore, the compounds of this invention may exist in unsolvated aswell as in solvated forms with pharmaceutically acceptable solvents suchas water, ethanol and the like.

The compounds of the present invention may have one or more asymmetriccentres and it is intended that any optical isomers (i.e. enantiomers ordiastereomers), as separated, pure or partially purified optical isomersand any mixtures thereof including racemic mixtures, i.e. a mixture ofstereoisomeres, are included within the scope of the invention.

In this context is understood that when specifying the enantiomericform, then the compound is in enantiomeric excess, e.g. essentially in apure form. Accordingly, one embodiment of the invention relates to acompound of the invention having an enantiomeric excess of at least 60%,at least 70%, at least 80%, at least 85%, at least 90%, at least 96%,preferably at least 98%.

Racemic forms may be resolved into the optical antipodes by knownmethods, for example, by separation of diastereomeric salts thereof withan optically active acid, and liberating the optically active aminecompound by treatment with a base. Separation of such diastereomericsalts can be achieved, e.g. by fractional crystallization. The opticallyactive acids suitable for this purpose may include, but are not limitedto d- or l-tartaric, mandelic or camphorsulfonic acids. Another methodfor resolving racemates into the optical antipodes is based uponchromatography on an optically active matrix. The compounds of thepresent invention may also be resolved by the formation andchromatographic separation of diastereomeric derivatives from chiralderivatizing reagents, such as, chiral alkylating or acylating reagents,followed by cleavage of the chiral auxiliary. Any of the above methodsmay be applied either to resolve the optical antipodes of the compoundsof the invention per se or to resolve the optical antipodes of syntheticintermediates, which can then be converted by methods described hereininto the optically resolved final products which are the compounds ofthe invention.

Additional methods for the resolution of optical isomers, known to thoseskilled in the art, may be used. Such methods include those discussed byJ. Jaques, A. Collet and S. Wilen in Enantiomers, Racemates, andResolutions, John Wiley and Sons, New York, 1981. Optically activecompounds can also be prepared from optically active starting materials.

The present invention further provides a pharmaceutical compositioncomprising a therapeutically effective amount of a compound of Formula Ior a pharmaceutically acceptable salt thereof and a pharmaceuticallyacceptable carrier. The present invention also provides a pharmaceuticalcomposition comprising a therapeutically effective amount of one of thespecific compounds disclosed in the Experimental Section and apharmaceutically acceptable carrier.

The compounds of the invention may be administered alone or incombination with pharmaceutically acceptable carriers or excipients, ineither single or multiple doses. The pharmaceutical compositionsaccording to the invention may be formulated with pharmaceuticallyacceptable carriers or diluents as well as any other known adjuvants andexcipients in accordance with conventional techniques such as thosedisclosed in Remington: The Science and Practice of Pharmacy, 22^(th)Edition, Gennaro, Ed., Mack Publishing Co., Easton, Pa., 2013.

Pharmaceutical compositions for oral administration include solid dosageforms such as capsules, tablets, dragees, pills, lozenges, powders andgranules. Where appropriate, the compositions may be prepared withcoatings such as enteric coatings or they may be formulated so as toprovide controlled release of the active ingredient such as sustained orprolonged release according to methods well known in the art. Liquiddosage forms for oral administration include solutions, emulsions,suspensions, syrups and elixirs. Pharmaceutical compositions forparenteral administration include sterile aqueous and nonaqueousinjectable solutions, dispersions, suspensions or emulsions as well assterile powders to be reconstituted in sterile injectable solutions ordispersions prior to use. Other suitable administration forms include,but are not limited to, suppositories, sprays, ointments, creams, gels,inhalants, dermal patches and implants.

Typical oral dosages range from about 0.01 to about 100 mg/kg bodyweight per day.

The compounds of this invention are generally utilized as the free baseor as a pharmaceutically acceptable salt thereof. A pharmaceuticallyacceptable salt of a compound of Formula I is prepared e.g. in aconventional manner by treating a solution or suspension of a free baseof Formula I with a molar equivalent of a pharmaceutically acceptableacid. Representative examples of suitable organic and inorganic acidsare described above.

Suitable pharmaceutical carriers include inert solid diluents orfillers, sterile aqueous solutions and various organic solvents.Examples of solid carriers include lactose, terra alba, sucrose,cyclodextrin, talc, gelatin, agar, pectin, acacia, magnesium stearate,stearic acid and lower alkyl ethers of cellulose. Examples of liquidcarriers include, but are not limited to, syrup, peanut oil, olive oil,phospholipids, fatty acids, fatty acid amines, polyoxyethylene andwater. Similarly, the carrier or diluent may include any sustainedrelease material known in the art, such as glyceryl monostearate orglyceryl distearate, alone or mixed with a wax. The pharmaceuticalcompositions formed by combining the compounds of Formula I or apharmaceutically acceptable salt thereof and a pharmaceuticallyacceptable carrier are readily administered in a variety of dosage formssuitable for the disclosed routes of administration. The formulationsmay conveniently be presented in unit dosage form by methods known inthe art of pharmacy.

If a solid carrier is used for oral administration, the preparation maybe tableted, placed in a hard gelatin capsule in powder or pellet formor it may be in the form of a troche or lozenge. The amount of solidcarrier will vary widely but will range from about 25 mg to about 1 gper dosage unit. If a liquid carrier is used, the preparation may be inthe form of a syrup, emulsion, soft gelatin capsule or sterileinjectable liquid such as an aqueous or non-aqueous liquid suspension orsolution.

The compounds of the present invention are as demonstrated in theexamples potent inhibitors of BACE1 and capable of lowering the level ofAβ peptide in rat brain and plasma, and said compounds are thus believedto be useful in the treatment of neurodegenerative and cognitivedisorders which pathological characteristics comprise Aβ deposits andneurofibrilary tangles, such as e.g. Alzheimer's disease. It may bebeneficial to combine a compound of the present invention with anothertreatment paradigm useful in the treatment of such disease, e.g.Alzheimer's disease.

Tau proteins are abundant in neurons. Tau proteins are soluble andhighly phosphorylation labile and bind to tubulin providing regulationand modulation of tubulin assembly, i.e. eventually the microtubularstructure and stability. Tau proteins can only associate with tubulin inthe most de-phosphorylated state, and phosphorylation/de-phosphorylationacts as a switch controlling the tubulin association. Phosphorylated Tauconstitutes an important part of the neurofibrillary tangles which areone of the hallmarks of Alzheimer's disease. The so-called Tauhypothesis suggests targeting these pathological tangles, a mainconstituent of which is phosphorylated Tau protein, as a treatmentparadigm for Alzheimer's disease. In particular, immunotherapies, bothactive and passive, have been suggested as a way to target Tauneurofibrillary tangles. In active immunotherapy, a pathogenic antigenis injected into the patient and the innate immune system elicits animmune response. This triggers the maturation of B-cells generating highaffinity antibodies against the administered antigen. In a passiveimmunotherapy, the triggering of the innate immune system iscircumvented by infusing a specific antibody against the antigen. It issuggested that the inherent clearance system then removes antibody boundligand. Substantial evidence for the efficacy of both active and passiveimmunotherapy targeting phosphorylated Tau protein as a treatment forAlzheimer's disease exists [Alzheimer's &Dementia, 7(4, suppl) S480-481;J Neurosci 30, 16559-16556, 2010; J Neurosci, 27, 9115-9129, 2007].

In one embodiment the invention provides a method for the treatment of aneurodegenerative or cognitive disorder, e.g. Alzheimer's disease, themethod comprising the administration of a therapeutically effect amountof two components (1) a compound of Formula I or a pharmaceuticallyacceptable salt thereof and (2) a compound useful in active or passiveTau immunotherapy to a patient in need thereof. Said compound useful inpassive Tau immunotherapy may be an antibody directed againstphosphorylated Tau protein. Said compound useful in active Tauimmunotherapy may be a fragment of the Tau protein amino acid sequencewhich upon injection in a patient elicits generation of ananti-phosphorylated Tau protein antibody in said patient. Theadministration according to this embodiment of the invention may besimultaneous, or there may be a time gap between the administration ofthe two components.

In one embodiment, the invention relates to the use of a compound ofFormula I or a pharmaceutically acceptable salt thereof and a compounduseful in active or passive Tau immunotherapy in the manufacture of amedicament for the treatment of neurodegenerative or cognitive disorder,e.g. Alzheimer's disease.

In one embodiment, the invention provides a compound of Formula I or apharmaceutically acceptable salt thereof and a compound useful in activeor passive Tau immunotherapy for use in a method for the treatment of aneurodegenerative or cognitive disorder, e.g. Alzheimer's disease.

In one embodiment, the invention provides a pharmaceutical compositioncomprising a compound of Formula I or a pharmaceutically acceptable saltthereof and a compound useful in active or passive Tau immunotherapy anda pharmaceutically acceptable carrier.

Another paradigm to treat neurodegenerative and cognitive disorder, e.g.Alzheimer's disease is to target the Aβ peptides. It has been suggestedthat this can be achieved by either passive or active immunotherapytargeting Aβ peptides [J Neurosci, 34, 11621-11630, 2014; J Neurosci 33,4923-4934, 2013]. In combination with compounds of the present inventionthis would attempt to target the same pathological mechanism via twodifferent routes. Anti-Aβ antibodies (either injected directly into thepatient or generated in the patient as a result of active immunotherapy)clear Aβ deposits in the brain, while further accumulation of Aβ peptideis blocked or reduced by the compounds of the present invention.

In one embodiment the invention provides a method for the treatment of aneurodegenerative or cognitive disorder, e.g. Alzheimer's disease, themethod comprising the administration of a therapeutically effect amountof two components (1) a compound of Formula I or a pharmaceuticallyacceptable salt thereof and (2) a compound useful in active or passiveAβ peptide immunotherapy to a patient in need thereof. Said compounduseful in passive Aβ peptide immunotherapy may be an anti-AP peptideantibody, such as gantenerumab, solanezumab, aducanumab or crenezumab.Said compound useful in active Aβ peptide immunotherapy may be afragment of the Aβ peptide amino acid sequence which upon injection intoa patient elicits anti-Aβ peptide antibodies in said patient. Theadministration according to this embodiment of the invention may besimultaneous, or there may be a time gap between the administration ofthe two components.

In one embodiment, the invention relates to the use of a compound ofFormula I or a pharmaceutically acceptable salt thereof and a compounduseful in active or passive Aβ peptide immunotherapy in the manufactureof a medicament for the treatment of neurodegenerative or cognitivedisorder, e.g. Alzheimer's disease.

In one embodiment, the invention provides a compound of Formula I or apharmaceutically acceptable salt thereof and a compound useful in activeor passive Aβ peptide immunotherapy for use in a method for thetreatment of a neurodegenerative or cognitive disorder, e.g. Alzheimer'sdisease.

In one embodiment, the invention provides a pharmaceutical compositioncomprising a compound of Formula I or a pharmaceutically acceptable saltthereof and a compound useful in active or passive Aβ peptideimmunotherapy and a pharmaceutically acceptable carrier.

The NMDA (N-Methyl-D-Aspartate) receptor antagonist memantine and theacetylcholine esterase inhibitors donepezil, rivastigmine andgalantamine are approved drugs for the treatment of Alzheimer's disease.

In one embodiment the invention provides a method for the treatment of aneurodegenerative or cognitive disorder, e.g. Alzheimer's disease, themethod comprising the administration of a therapeutically effect amountof two components (1) a compound of Formula I or a pharmaceuticallyacceptable salt thereof and (2) an NMDA receptor antagonist or anacetylcholine esterase inhibitor to a patient in need thereof. Theadministration according to this embodiment of the invention may besimultaneous, or there may be a time gap between the administration ofthe two components.

In one embodiment, the invention relates to the use of a compound ofFormula I or a pharmaceutically acceptable salt thereof and an NMDAreceptor antagonist or an acetylcholine esterase inhibitor in themanufacture of a medicament for the treatment of neurodegenerative orcognitive disorder, e.g. Alzheimer's disease.

In one embodiment, the invention provides a compound of Formula I or apharmaceutically acceptable salt thereof and an NMDA receptor antagonistor an acetylcholine esterase inhibitor for use in a method for thetreatment of a neurodegenerative or cognitive disorder, e.g. Alzheimer'sdisease.

In one embodiment, the invention provides a pharmaceutical compositioncomprising a compound of Formula I or a pharmaceutically acceptable saltthereof and an NMDA receptor antagonist or an acetylcholine esteraseinhibitor and a pharmaceutically acceptable carrier.

Seizures or epileptiform activity are also associated with Alzheimer'sdisease, including early stages of Alzheimer's disease, and treatment ofsaid epileptic activity, which seeks to normalise hippocampalhyperactivity, may form part of an Alzheimer's disease treatmentparadigm [JAMA Neurol, 70, 1158-1166, 2013; J Neurosci Res, 93, 454,465, 2015; Neuron, 74, 647-474, 2012; Neurepsychpharm, 35, 1016-1025,2010; CNS Neurosci Ther, 19, 871-881, 2013]. Useful antiepilepticsinclude NMDA receptor antagonists and ion channel modulators, such astopiramate, levetiracetam and lamotrigine.

In one embodiment the invention provides a method for the treatment of aneurodegenerative or cognitive disorder, e.g. Alzheimer's disease, themethod comprising the administration of a therapeutically effect amountof two components (1) a compound of Formula I or a pharmaceuticallyacceptable salt thereof and (2) an antiepileptic to a patient in needthereof. The administration according to this embodiment of theinvention may be simultaneous, or there may be a time gap between theadministration of the two components.

In one embodiment, the invention relates to the use of a compound ofFormula I or a pharmaceutically acceptable salt thereof and anantiepileptic in the manufacture of a medicament for the treatment ofneurodegenerative or cognitive disorder, e.g. Alzheimer's disease.

In one embodiment, the invention provides a compound of Formula I or apharmaceutically acceptable salt thereof and an antiepileptic for use ina method for the treatment of a neurodegenerative or cognitive disorder,e.g. Alzheimer's disease.

In one embodiment, the invention provides a pharmaceutical compositioncomprising a compound of Formula I or a pharmaceutically acceptable saltthereof and an antiepileptic and a pharmaceutically acceptable carrier.

Emerging evidence suggests that inflammation has a causal role inAlzheimer's disease pathogenesis and that neuroinflammation is not apassive system activated by emerging β-amyloid deposits andneurofibrilary tangles, but also contributes to pathogenesis itself[Lancet Neurol, 14, 388-405, 2015; J Alz Dis, 44, 385-396, 2015; Neurol,84, 2161-2168, 2015]. It follows from this that anti-inflammatory drugs,such as NSAID (non-steroid anti-inflammatory drugs), TNFα inhibitors,such as etanercept and p38 MAP kinase inhibitors, such as VX-745(5-(2,6-Dichlorophenyl)-2-((2,4-difluorophenyl)thio)-6H-pyrimido[1,6-b]pyridazin-6-one)may be useful in the treatment of Alzheimer's disease.

In one embodiment the invention provides a method for the treatment of aneurodegenerative or cognitive disorder, e.g. Alzheimer's disease, themethod comprising the administration of a therapeutically effect amountof two components (1) a compound of Formula I or a pharmaceuticallyacceptable salt thereof and (2) an anti-inflammatory drug to a patientin need thereof. The administration according to this embodiment of theinvention may be simultaneous, or there may be a time gap between theadministration of the two components.

In one embodiment, the invention relates to the use of a compound ofFormula I or a pharmaceutically acceptable salt thereof andanti-inflammatory drug in the manufacture of a medicament for thetreatment of neurodegenerative or cognitive disorder, e.g. Alzheimer'sdisease.

In one embodiment, the invention provides a compound of Formula I or apharmaceutically acceptable salt thereof and an anti-inflammatory drugfor use in a method for the treatment of a neurodegenerative orcognitive disorder, e.g. Alzheimer's disease.

In one embodiment, the invention provides a pharmaceutical compositioncomprising a compound of Formula I or a pharmaceutically acceptable saltthereof and an anti-inflammatory drug and a pharmaceutically acceptablecarrier.

In addition, efficacy in the treatment of Alzheimer's disease has beendemonstrated for Tau protein aggregation inhibitors, such as TRX-0237,also known as Methylene Blue, and SSRIs (Selective Serotonin ReuptakeInhibitor), such as citalopram [Behav Pharmacol, 26, 353-368, 2015; SciTransl Med, 6(236re4), 2014].

In one embodiment the invention provides a method for the treatment of aneurodegenerative or cognitive disorder, e.g. Alzheimer's disease, themethod comprising the administration of a therapeutically effect amountof two components (1) a compound of Formula I or a pharmaceuticallyacceptable salt thereof and (2) Tau protein aggregation inhibitor or anSSRI to a patient in need thereof. The administration according to thisembodiment of the invention may be simultaneous, or there may be a timegap between the administration of the two components.

In one embodiment, the invention relates to the use of a compound ofFormula I or a pharmaceutically acceptable salt thereof and a Tauprotein aggregation inhibitor or an SSRI in the manufacture of amedicament for the treatment of neurodegenerative or cognitive disorder,e.g. Alzheimer's disease.

In one embodiment, the invention provides a compound of Formula I or apharmaceutically acceptable salt thereof and a Tau protein aggregationinhibitor or an SSRI drug for use in a method for the treatment of aneurodegenerative or cognitive disorder, e.g. Alzheimer's disease.

In one embodiment, the invention provides a pharmaceutical compositioncomprising a compound of Formula I or a pharmaceutically acceptable saltthereof and a Tau protein aggregation inhibitor or an SSRI drug and apharmaceutically acceptable carrier.

EXPERIMENTAL SECTION

The compounds of the present invention of the general formula I, whereinR¹ and Ar are as defined above can be prepared by the methods outlinedin the following reaction schemes 1-7 and in the examples. In thedescribed methods, it is possible to make use of variants ormodifications, which are themselves known to chemists skilled in the artor could be apparent to the person of ordinary skill in this art.Furthermore, other methods for preparing compounds of the invention willbe readily apparent to the person skilled in the art in light of thefollowing reaction schemes and examples.

For example, Scheme 2 describe the use of selective protecting groupsduring the synthesis of the compounds of the invention. One skilled inthe art would be able to select the appropriate protecting group for aparticular reaction. Moreover, it may be necessary to incorporateprotection and deprotection strategies for substituents such as amino,amido, keto and hydroxyl groups in the synthetic methods described belowto synthesize the compounds of Formula I. Methods for protection anddeprotection of such groups are well known in the art, and may be foundin T. Green, et al., Protective Groups in Organic Synthesis, 1991,2^(nd) Edition, John Wiley & Sons, New York.

For compounds, which can exist as a mixture or equilibrium between twoor more tautomers, only one tautomer is represented in the schemes,although it may not be the most stable tautomer. For compounds, whichcan exist in enantiomeric, stereoisomeric or geometric isomeric formstheir geometric configuration is specified; otherwise the structurerepresents a mixture of stereoisomers.

Analytical LC-MS data was obtained using the following methods.

Method A:

LC-MS was run on Waters Aquity UPLC-MS consisting of Waters Aquityincluding column manager, binary solvent manager, sample organizer, PDAdetector (operating at 254 nm), ELS detector, and SQ-MS equipped withAPPI-source operating in positive ion mode.

LC-conditions: The column was Acquity UPLC BEH C18 1.7 μm; 2.1×150 mmoperating at 60° C. with 0.6 ml/min of a binary gradient consisting ofwater+0.05% trifluoroacetic acid (A) and acetonitrile+5% water+0.03%trifluoroacetic acid (B). Gradient: 0.00 min: 10% B; 3.00 min: 99.9% B;3.01 min: 10% B; 3.60 min: 10% B. Total run time: 3.60 min.

Method B:

LC-MS was run on Waters Acquity UPLC-MS consisting of Waters Acquityincluding column manager, binary solvent manager, sample organizer, PDAdetector (operating at 254 nm), ELS detector, and TQ-MS equipped withAPPI-source operating in positive ion mode.

LC-conditions: The column was Acquity UPLC BEH C18 1.7 μm; 2.1×50 mmoperating at 60° C. with 1.2 ml/min of a binary gradient consisting ofwater+0.05% trifluoroacetic acid (A) and acetonitrile+5% water+0.05%trifluoroacetic acid (B). Gradient: 0.00 min: 10% B; 1.00 min: 100% B;1.01 min: 10% B; 1.15 min: 10% B. Total run time: 1.15 min.

¹H NMR spectra were recorded at 600 MHz on a Bruker Avance AV-III-600instrument or at 400 MHz on a Bruker Avance AV-III-400 instrument or aVarian 400 instrument. Chemical shift values are expressed in ppm-valuesrelative. The following abbreviations are used for multiplicity of NMRsignals: s=singlet, d=doublet, t=triplet, q=quartet, dd=double doublet,ddd=double double doublet, dt=double triplet, br=broad, and m=multiplet.

Compounds of the general formulae VIa and VIb may be prepared as shownin Scheme 1.

where R¹ is as defined under formula I and R² is as an alkyl group suchas methyl or ethyl.

Compounds of the general formula IV (Scheme 1) may be prepared byreacting compounds of formula II with a sulfinamide such as III in thepresence of a Lewis acid/drying agent such as titanium tetraethoxide.Treatment of compounds of the formula IV with compounds of the generalformula V such as ethyl bromofluoroacetate in the presence of Zn powderor in the presence of diethyl zinc andtris(triphenylphosphine)rhodium(I) chloride gives compounds of thegeneral formulae VIa and VIb which can be separated by chromatography.

Compounds of the general formulae XIIa and XIIb may be prepared as shownin Scheme 2.

where R² and R³ are alkyl groups such as methyl or ethyl and R⁴ isprotecting group such as tert-butoxy carbonyl.

Compounds of formula VII (Scheme 2) may be prepared by treatment ofcompounds of formula VIa with a reducing agent such asdiisobutylaluminium hydride. In some cases, compound VII might be inequilibrium with the hydrate form. Treatment of compounds of the generalformula VII with conditions such as ethyl2-(diethoxyphosphoryl)-2-fluoroacetate in the presence of lithiumchloride and a base such as N,N-diisopropylethylamine gives compounds ofthe general formula VIII as either the E or Z form or a mixture thereof.Compounds of the general formula IX are obtained by hydrogenation ofcompounds of the general formula VIII in the presence of a catalyst suchas palladium on carbon. Compounds of the general formula X are obtainedby treatment of compounds of the general formula IX with an acid such ashydrochloric acid in methanol followed by heating the intermediate in ahigher boiling solvent such as toluene or xylenes in the presence of abase such as triethylamine. Compounds of the general formula XI areobtained by treatment of compounds of the general formula X withdi-tert-butyl dicarbonate in the presence of a catalytic amount ofN,N-dimethyl-4-amino-pyridine. Compounds of the general formulae XIIaand XIIb are obtained by treatment of compounds of the general formulaXI with a base such as lithium hexamethyldisilazide followed byalkylation with an alkylhalide. The same procedures described above canalso be used for the synthesis of compounds of the general formulae XIIcand XIId starting from VIb.

As an example and wherein R¹ is fluorine in the 2-position of the phenylring or wherein the phenyl ring is substituted with two fluorines in the2- and 3-positions, compound of the general formula XVIIa may beprepared as shown in Scheme 3.

where R⁴ is a protecting group such as tert-butoxy carbonyl.

Compounds of the general formula XIIIa are obtained by treatingcompounds of the general formula XIIa with nitric acid. This will bothdeprotect the amide moiety and nitrate the benzene ring in the indicatedposition. Reduction of the nitro group of compounds of the generalformula XIIIa followed by protection of the formed aniline moiety givescompounds of the general formula XVa. Treatment of compounds of thegeneral formula XVa with a reagent such as Lawesson's reagent(2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide)gives compounds of the general formula XVIa. Deprotection of XVIa underconditions such as trifluoroacetic acid in dichloromethane givescompound XVIIa. Alternatively, the order of reactions can be changed andcompounds of the general formula XIIIa can be reacted with a reagentsuch as Lawesson's reagent to give compounds of the general formulaXXIa, which after reduction of the nitro group also gives compounds ofthe general formula XVIIa (Scheme 4).

As an example and wherein R¹ is fluorine in the ortho position of thephenyl ring or wherein the phenyl ring is substituted with two fluorinesin the 2- and 3-positions, compound of the general formula XVIIb (Scheme5) may be prepared by the same procedures as shown in Scheme 3 and 4 butstarting from compound of general formula XIIb. Likewise, the sameprocedures can be used for the synthesis of compounds of the generalformulae XVIIc and XVIId starting from XIIc and XIId, respectively.

where R⁴ is a protecting group such as tert-butoxy carbonyl.

Compounds of the general formula XIIIa may also be prepared as shown inScheme 6. Starting from nitro substituted acetophenones of generalformula IIb, compounds of the general formula VIII may be prepared asdescribed in Schemes 1 and 2. Compounds of the general formula IX may beobtained by selective reduction of the olefin moiety of compounds of thegeneral formula VIII. Compounds of the general formula XIIIa may beprepared as described for compounds of general formula XIIa in Scheme 2.Likewise, compounds of general formulae XIIIb, XIIIc and XIIId may alsobe prepare as shown in Scheme 6 starting from nitro substitutedacetophenones of general formula IIb.

where R¹ is as defined under formula I and R³ is an alkyl group such asmethyl or ethyl

Compounds of the general formula I may be prepared as shown in Scheme 7.

where R¹ and Ar are as defined under formula I.

Compounds of the general formula XX (Scheme 7) may be prepared byreacting compounds of the general formula XVII with a carboxylic acidchloride of general formula XVIII or by reaction with a carboxylic acidof general formula XIX using procedures known to chemists skilled in theart. Treatment of compounds of the general formula XX with ammonia givescompounds of the general formula I. In some cases, the addition of andoxidizing reagent such as tert-butyl hydroperoxide might be necessary tofacilitate the reaction.

Preparation of Intermediates Intermediate:(R)—N-[1-(2-fluorophenyl)ethylidene]-2-methyl-propane-2-sulfinamide

To a solution of 1-(2-fluorophenyl)ethanone (100 g, 723.9 mmol) and(R)-2-methylpropane-2-sulfinamide (105.28 g, 868.68 mmol) in THF (2.00L) was added tetraethoxytitanium (330.26 g, 1.45 mol). The solution waswarmed to 80° C. and stirred for 18 hours. The reaction was quenched bywater (500 mL), then extracted with ethyl acetate (500 mL, 4 times). Thecombined organic phases were washed with brine (500 mL), dried overanhydrous Na₂SO₄, filtered and concentrated in vacuo. The residue waspurified by silica gel chromatography (column height: 250 mm, diameter:100 mm, 100-200 mesh silica gel, petroleum ether/ethyl acetate=10/1,5/1) to give(R)—N-[1-(2-fluorophenyl)ethylidene]-2-methyl-propane-2-sulfinamide (150g, 86% yield).

Intermediates: Ethyl(2R,3R)-3-[[(R)-tert-butylsulfinyl]amino]-2-fluoro-3-(2-fluorophenyl)-butanoateand ethyl(2S,3R)-3-[[(R)-tert-butylsulfinyl]amino]-2-fluoro-3-(2-fluorophenyl)butanoate

To a suspension of(R)—N-[1-(2-fluorophenyl)ethylidene]-2-methyl-propane-2-sulfinamide (20.g, 82.9 mmol), ethyl 2-bromo-2-fluoro-acetate (30.66 g, 165.8 mmol) andRh(PPh₃)₃Cl (2.30 g, 2.49 mmol) in anhydrous THF (400 mL) was addedEt₂Zn (1M in THF, 249 mL) dropwise at 0° C. over a period of 10 minutesunder argon during which the temperature was maintained below 5° C. Thereaction mixture was warmed to 30° C. and stirred at 30° C. for 18hours. The reaction was quenched with water (150 mL), filtered and thenextracted with ethyl acetate (3×500 mL). The combined organic phaseswere washed with saturated brine (40 mL), dried over anhydrous Na₂SO₄,filtered and concentrated in vacuo. The residue was purified by flashchromatography on silica gel (petroleum ether:ethyl acetate=100:1 to3:1) to give ethyl(2R,3R)-3-[[(R)-tert-butylsulfinyl]amino]-2-fluoro-3-(2-fluorophenyl)butanoate(11.2 g, 39% yield) and an impure fraction containing(2S,3R)-3-[[(R)-tert-butylsulfinyl]amino]-2-fluoro-3-(2-fluorophenyl)butanoate.After preparative HPLC purification of the latter fraction,(2S,3R)-3-[[(R)-tert-butylsulfinyl]amino]-2-fluoro-3-(2-fluorophenyl)butanoatewas isolated (0.8 g, 3% yield).

Ethyl(2R,3R)-3-(((R)-tert-butylsulfinyl)amino)-3-(2,3-difluorophenyl)-2-fluorobutanoatewas prepared in a similar way starting from(R)—N-[1-(2,3-difluorophenyl)ethylidene]-2-methyl-propane-2-sulfinamide

Intermediate: Ethyl(4S,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2-fluorophenyl)hex-2-enoate

To a solution of ethyl(2R,3R)-3-[[(R)-tert-butylsulfinyl]amino]-2-fluoro-3-(2-fluorophenyl)butanoate(10.0 g, 28.8 mmol) in THF (200 mL) was added DIBAL-H(diisobutylaluminium hydride) (1M in THF, 143.9 mL) dropwise at −78° C.over a period of 30 minutes under N₂. The yellow reaction solution wasstirred at −78° C. for 3.5 hours. The reaction was quenched with water(200 mL), filtered and extracted with ethyl acetate (200 mL, 4 times).The combined organic phases were washed with saturated brine (200 mL),dried over anhydrous Na₂SO₄, filtered and concentrated in vacuo to givethe crude product(R)—N-((2R,3R)-3-fluoro-2-(2-fluorophenyl)-4-oxobutan-2-yl)-2-methylpropane-2-sulfinamide(8.0 g, crude). To a suspension of ethyl2-diethoxyphosphoryl-2-fluoro-acetate (5.13 g, 21.2 mmol), DIPEA(N,N-diisopropylethylamine) (1.18 g, 9.1 mmol) and LiCl (386 mg, 9.1mmol) in acetonitrile (150 mL) was added a solution of(R)—N-((2R,3R)-3-fluoro-2-(2-fluorophenyl)-4-oxobutan-2-yl)-2-methylpropane-2-sulfinamide(2.30 g, 7.58 mmol) in acetonitrile (20 mL) dropwise at 0° C. over aperiod of 10 minutes under N₂. The suspension was warmed to 25° C.stirred for 18 hours. The reaction was concentrated in vacuo, theresidue was extracted with ethyl acetate (100 mL, 3 times). The combinedorganic phases were washed with saturated brine (100 mL), dried overanhydrous Na₂SO₄, filtered and concentrated in vacuo. The residue waspurified by flash chromatography on silica gel (petroleum ether/ethylacetate=5:1, 1:1) to give ethyl(4S,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2-fluorophenyl)hex-2-enoate(3.44 g, 8.79 mmol, 49.8% yield).

Ethyl(4R,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2-fluorophenyl)hex-2-enoatewas prepared in a similar way starting from(2S,3R)-3-[[(R)-tert-butylsulfinyl]amino]-2-fluoro-3-(2-fluorophenyl)butanoate

Ethyl(4S,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2,3-difluorophenyl)hex-2-enoatewas prepared in a similar way starting from ethyl(2R,3R)-3-(((R)-tert-butylsulfinyl)amino)-3-(2,3-difluorophenyl)-2-fluorobutanoate

Intermediate: Ethyl(4S,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2-fluorophenyl)-hexanoate

To a solution of ethyl(4S,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2-fluorophenyl)hex-2-enoate(13.77 g, 35.18 mmol) in ethyl acetate (500 mL) was added Pd/C (10%,2.00 g, wet). The black suspension was degassed under vacuum and purgedwith H₂ several times. The mixture was stirred under H₂ (50 psi) at 30°C. for 18 hours. The suspension was filtered and the filter wasconcentrated to give product of ethyl(4S,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2-fluorophenyl)hexanoate(10.5 g, 75.9% yield).

Ethyl(4R,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2-fluorophenyl)hexanoatewas prepared in a similar way starting from ethyl(4R,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2-fluorophenyl)hex-2-enoate

Ethyl(4S,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2,3-difluorophenyl)hexanoatewas prepared in a similar way starting from ethyl(4S,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2,3-difluorophenyl)hex-2-enoate

Intermediate:(5S,6R)-3,5-difluoro-6-(2-fluorophenyl)-6-methylpiperidin-2-one

To a solution of ethyl(4S,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2-fluorophenyl)-hexanoate(10.50 g, 26.69 mmol) in MeOH (100 mL) was added HC/MeOH (4 M, 50 mL) inone portion at 30° C. under N₂. The colorless solution was stirred at30° C. for 2 hours. The solution was concentrated in vacuum to givecrude ethyl (4S,5S)-5-amino-2,4-difluoro-5-(2-fluorophenyl)hexanoate(6.50 g, 21.35 mmol, 80% yield) which was dissolved in toluene (100 mL)and triethylamine (2.19 g, 21.64 mmol) was added. The colorless solutionwas stirred at 110° C. for 18 hours. The reaction was concentrated invacuo, the residue was purified by flash chromatography on silica gel(petroleum ether:ethyl acetate=3:1-1:1) to give(5S,6R)-3,5-difluoro-6-(2-fluorophenyl)-6-methyl-piperidin-2-one (4.50g, 17.6 mmol, 78.2% yield).

(5R,6R)-3,5-difluoro-6-(2-fluorophenyl)-6-methylpiperidin-2-one wasprepared in a similar way starting from(4R,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2-fluorophenyl)hexanoate.

(5S,6R)-3,5-difluoro-6-(2,3-difluorophenyl)-6-methylpiperidin-2-one wasprepared in a similar way starting from(4S,5R)-5-[[(R)-tert-butylsulfinyl]amino]-2,4-difluoro-5-(2,3-difluorophenyl)hexanoate

Intermediate: tert-Butyl(2R,3S)-3,5-difluoro-2-(2-fluorophenyl)-2-methyl-6-oxo-piperidine-1-carboxylate

To a solution of(5S,6R)-3,5-difluoro-6-(2-fluorophenyl)-6-methyl-piperidin-2-one (4.50g, 18.50 mmol) and di-tert-butyl dicarbonate (8.08 g, 37.0 mmol) in THF(100 mL) was added N,N-dimethylpyridin-4-amine (113 mg, 925 μmol) in oneportion at 25° C. under N₂. The colorless solution was stirred at 25° C.for 48 hours. The solution was quenched with water (100 mL) andextracted with ethyl acetate (100 mL, 3 times). The combined organicphases were washed with saturated brine (50 mL), dried with anhydrousNa₂SO₄, filtered and concentrated in vacuum. The residue was purified byflash chromatography on silica gel (petroleum ether/ethyl acetate=20/1,5/1) to give tert-butyl(2R,3S)-3,5-difluoro-2-(2-fluorophenyl)-2-methyl-6-oxo-piperidine-1-carboxylate(4.70 g, 13.0 mmol, 70.3% yield).

tert-Butyl(2R,3R)-3,5-difluoro-2-(2-fluorophenyl)-2-methyl-6-oxo-piperidine-1-carboxylatewas prepared in a similar way starting from(5R,6R)-3,5-difluoro-6-(2-fluorophenyl)-6-methylpiperidin-2-one.

tert-Butyl(2R,3S)-3,5-difluoro-2-(2,3-difluorophenyl)-2-methyl-6-oxo-piperidine-1-carboxylatewas prepared in a similar way starting from(5S,6R)-3,5-difluoro-6-(2,3-difluorophenyl)-6-methylpiperidin-2-one

Intermediates: tert-butyl(2R,3S,5R)-3,5-difluoro-2-(2-fluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylateand tert-butyl(2R,3S,5S)-3,5-difluoro-2-(2-fluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylate

To a solution of tert-butyl(2R,3S)-3,5-difluoro-2-(2-fluorophenyl)-2-methyl-6-oxo-piperidine-1-carboxylate(1.50 g, 4.37 mmol) in THF (30 mL) was added LiHMDS (Lithiumbis(trimethylsilyl)amide) (1 M, 8.74 mL) dropwise at −78° C. over aperiod of 10 minutes under N₂. The solution was stirred at −78° C. for 1hour, then to the solution was added iodomethane (3.10 g, 21.9 mmol).The reaction solution was stirred at −78° C. for another 45 minutes.Then the solution was allowed to be warmed to 25° C. and stirred for 18hours. The reaction was slowly quenched by ice and then extracted withethyl acetate (30 mL, 3 times). The combined organic phases were washedwith saturated brine (30 mL, twice), dried over anhydrous Na₂SO₄,filtered and concentrated in vacuo. The residue was purified by flashchromatography on silica gel (petroleum ether:ethyl acetate=15:1, 10:1)to give the products tert-butyl(2R,3S,5R)-3,5-difluoro-2-(2-fluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylate(550 mg, 1.54 mmol, 35.2% yield) and tert-butyl(2R,3S,5S)-3,5-difluoro-2-(2-fluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylate(600 mg, 1.68 mmol, 38.4% yield).

tert-butyl(2R,3R,5S)-3,5-difluoro-2-(2-fluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylatewas prepared in a similar way starting from tert-butyl(2R,3R)-3,5-difluoro-2-(2-fluorophenyl)-2-methyl-6-oxo-piperidine-1-carboxylate

tert-butyl(2R,3S,5R)-3,5-difluoro-2-(2,3-difluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylateand tert-butyl(2R,3S,5S)-3,5-difluoro-2-(2,3-difluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylatewere prepared in a similar way starting from tert-butyl(2R,3S)-3,5-difluoro-2-(2,3-difluorophenyl)-2-methyl-6-oxo-piperidine-1-carboxylate

Intermediate:(3R,5S,6R)-3,5-Difluoro-6-(2-fluoro-5-nitro-phenyl)-3,6-dimethyl-piperidin-2-one

tert-Butyl-(2R,3S,5R)-3,5-difluoro-2-(2-fluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylate(1.20 g, 3.36 mmol) in trifluoroacetic acid (5.69 mL, 73.9 mmol) wasadded H₂SO₄ (1.27 mL, 25.9 mmol), then to the solution was added HNO₃(1.16 mL, 16.8 mmol), the solution was stirred at 0° C. for 30 min, thenthe solution was stirred at 50° C. for 18 hours, LCMS showed no startingmaterial, the solution was poured into ice-water (w/w=1/1) (50 mL) andbasified to pH>11 using 5N aqueous NaOH. The aqueous phase was extractedwith ethyl acetate (50 mL, 3 times). The combined organic phases werewashed with saturated brine (100 mL), dried with anhydrous Na₂SO₄,filtered and concentrated in vacuum. The residue was purified by flashchromatography on silica gel (petroleum ether/ethyl acetate=10/1, 2/1)to give(3R,5S,6R)-3,5-difluoro-6-(2-fluoro-5-nitro-phenyl)-3,6-dimethyl-piperidin-2-one(1.0 g, 99% yield).

(3S,5S,6R)-3,5-difluoro-6-(2-fluoro-5-nitrophenyl)-3,6-dimethylpiperidin-2-onewas prepared in a similar way starting from tert-butyl(2R,3S,5S)-3,5-difluoro-2-(2-fluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylate.

(3S,5R,6R)-3,5-difluoro-6-(2-fluoro-5-nitrophenyl)-3,6-dimethylpiperidin-2-onewas prepared in a similar way starting from tert-butyl(2R,3R,5S)-3,5-difluoro-2-(2-fluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylate.

(3R,5S,6R)-3,5-difluoro-6-(2,3-difluoro-5-nitrophenyl)-3,6-dimethylpiperidin-2-onewas prepared in a similar way starting from tert-butyl(2R,3S,5R)-3,5-difluoro-2-(2,3-difluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylate.

(3S,5S,6R)-3,5-difluoro-6-(2,3-difluoro-5-nitrophenyl)-3,6-dimethylpiperidin-2-onewas prepared in a similar way starting from tert-butyl(2R,3S,5S)-3,5-difluoro-2-(2,3-difluorophenyl)-2,5-dimethyl-6-oxo-piperidine-1-carboxylate.

Intermediate:(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidin-2-one

To a solution of(3R,5S,6R)-3,5-difluoro-6-(2-fluoro-5-nitro-phenyl)-3,6-dimethyl-piperidin-2-one(1.10 g, 3.64 mmol) in ethyl acetate (100 mL) was added Pd/C (10%, wet,0.5 g) under N₂. The suspension was degassed under vacuum and purgedwith H₂ several times. The mixture was stirred under H₂ (15 psi) at 25°C. for 18 hours. The reaction mixture was filtered and the filtrate wasconcentrated to give

(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidin-2-one(950 mg, 3.49 mmol, 96% yield).

(3S,5S,6R)-6-(5-amino-2-fluorophenyl)-3,5-difluoro-3,6-dimethylpiperidin-2-onewas prepared in a similar way starting from(3S,5S,6R)-3,5-difluoro-6-(2-fluoro-5-nitrophenyl)-3,6-dimethylpiperidin-2-one.

Intermediate: tert-ButylN-[3-[(2R,3S,5R)-3,5-difluoro-2,5-dimethyl-6-oxo-2-piperidyl]-4-fluoro-phenyl]carbamate

To a mixture of(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidin-2-one(750 mg, 2.75 mmol) in aqueous NaHCO₃(5 mL) and dichloromethane (20 mL)was added di-tert-butyl dicarbonate (1.80 g, 8.26 mmol) in one portionat 25° C. under N₂. The colorless mixture was stirred at 25° C. for 18hours. The mixture was quenched with water (20 mL) and extracted withethyl acetate (50 mL, 3 times). The combined organic phases were washedwith saturated brine (50 mL, twice), dried with anhydrous Na₂SO₄,filtered and concentrated in vacuum. The residue was purified by flashchromatography on silica gel (petroleum ether/ethyl acetate=10/1, 1/1)to give tert-butylN-[3-[(2R,3S,5R)-3,5-difluoro-2,5-dimethyl-6-oxo-2-piperidyl]-4-fluoro-phenyl]carbamate(850 mg, 83% yield).

tert-ButylN-[3-[(2R,3S,5S)-3,5-difluoro-2,5-dimethyl-6-oxo-2-piperidyl]-4-fluoro-phenyl]carbamatewas prepared in a similar way starting from(3S,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidin-2-one.

Intermediate: tert-ButylN-[3-[(2R,3S,5R)-3,5-difluoro-2,5-dimethyl-6-thioxo-2-piperidyl]-4-fluoro-phenyl]carbamate

To a suspension of tert-butylN-[3-[(2R,3S,5R)-3,5-difluoro-2,5-dimethyl-6-oxo-2-piperidyl]-4-fluoro-phenyl]carbamate(250 mg, 671 μmol) in toluene (10 mL) was added Lawesson's reagent(2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide)(149 mg, 369 μmol) in one portion at 90° C. under N₂. The mixture wasstirred at 90° C. for 1 hour. The mixture was concentrated in reducedpressure. The residue was purified by flash chromatography on silica gel(petroleum ether/ethyl acetate=10/1, 1/1) to give tert-butylN-[3-[(2R,3S,5R)-3,5-difluoro-2,5-dimethyl-6-thioxo-2-piperidyl]-4-fluoro-phenyl]carbamate(230 mg, 88% yield).

tert-butylN-[3-[(2R,3S,5S)-3,5-difluoro-2,5-dimethyl-6-thioxo-2-piperidyl]-4-fluoro-phenyl]carbamatewas prepared in a similar way starting from tert-butylN-[3-[(2R,3S,5S)-3,5-difluoro-2,5-dimethyl-6-oxo-2-piperidyl]-4-fluoro-phenyl]carbamate.

Intermediate:(3R,5S,6R)-6-(5-Amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thione

To a solution of tert-butylN-[3-[(2R,3S,5R)-3,5-difluoro-2,5-dimethyl-6-thioxo-2-piperidyl]-4-fluoro-phenyl]carbamate(500 mg, 1.29 mmol) in dichloromethane (20 mL) was added HCl/MeOH (10mL) in one portion at 25° C. under N₂. The mixture was stirred at 25° C.for 18 hours. The mixture was concentrated in reduced pressure. Theresidue was dissolved in water (10 mL), the pH of the solution wasbasified to pH=7-8 using saturated aqueous NaHCO₃ solution, the aqueousphase was extracted with ethyl acetate (20 mL, 3 times). The combinedorganic phases were washed with saturated brine (20 mL, twice), driedwith anhydrous Na₂SO₄, filtered and concentrated in vacuum. The residuewas purified by flash chromatography on silica gel (petroleumether/ethyl acetate=10/1, 1/1) to give

(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thione(318 mg, 85.5% yield).

(3S,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thionewas prepared in a similar way starting from tert-butylN-[3-[(2R,3S,5S)-3,5-difluoro-2,5-dimethyl-6-thioxo-2-piperidyl]-4-fluoro-phenyl]carbamate.

Intermediate:(3S,5S,6R)-3,5-difluoro-6-(2-fluoro-5-nitrophenyl)-3,6-dimethylpiperidine-2-thione

To a suspension of(3S,5S,6R)-3,5-difluoro-6-(2-fluoro-5-nitrophenyl)-3,6-dimethylpiperidin-2-one(4.50 g, 14.89 mmol) in toluene (100 mL) was added Lawesson's reagent(3.31 g, 8.19 mol) in one portion at 90° C. under N₂. The mixture wasstirred at 90° C. for 2 hours. The mixture was concentrated in vacuo.The residue was purified by flash chromatography on silica gel(petroleum ether/ethyl acetate) to give(3S,5S,6R)-3,5-difluoro-6-(2-fluoro-5-nitrophenyl)-3,6-dimethylpiperidine-2-thione(4.0 g, 84% yield).

(3S,5R,6R)-3,5-difluoro-6-(2-fluoro-5-nitrophenyl)-3,6-dimethylpiperidine-2-thionewas prepared in a similar way starting from(3S,5R,6R)-3,5-difluoro-6-(2-fluoro-5-nitrophenyl)-3,6-dimethylpiperidin-2-one.

(3S,5S,6R)-6-(2,3-difluoro-5-nitrophenyl)-3,5-difluoro-3,6-dimethylpiperidine-2-thionewas prepared in a similar way starting from(3S,5S,6R)-6-(2,3-difluoro-5-nitrophenyl)-3,5-difluoro-3,6-dimethylpiperidin-2-one.

(3R,5S,6R)-6-(2,3-difluoro-5-nitrophenyl)-3,5-difluoro-3,6-dimethylpiperidine-2-thionewas prepared in a similar way starting from(3R,5S,6R)-6-(2,3-difluoro-5-nitrophenyl)-3,5-difluoro-3,6-dimethylpiperidin-2-one.

Intermediate:(3S,5S,6R)-6-(5-amino-2-fluorophenyl)-3,5-difluoro-3,6-dimethylpiperidine-2-thione

To a solution of(3S,5S,6R)-3,5-difluoro-6-(2-fluoro-5-nitrophenyl)-3,6-dimethylpiperidine-2-thione(4.50 g, 14.14 mmol) and NH₄Cl (3.78 g, 70.70 mmol) in ethanol (80 mL)and water (20 mL) was added iron powder (3.95 g, 70.70 mmol) in oneportion at 25° C. under N₂. The black suspension was stirred at 25° C.for 18 hours. The mixture was filtered and the filtrate was concentratedin reduced pressure. The residue was extracted with ethyl acetate (100mL×3). The combined organic phases were washed with saturated brine (100mL), dried with anhydrous Na₂SO₄, filtered and concentrated in vacuo.The residue was purified by flash chromatography on silica gel(petroleum ether/ethyl acetate) to give(3S,5S,6R)-6-(5-amino-2-fluorophenyl)-3,5-difluoro-3,6-dimethylpiperidine-2-thione(2.59 g, 61% yield). ¹H NMR (CDCl₃ 400 MHz TMS): δ 8.33 (s, 1H),6.93-6.87 (m, 1H), 6.62-6.60 (m, 1H), 6.45-6.44 (m, 1H), 5.38-5.26 (m,1H), 3.73 (s, 2H), 2.65-2.58 (m, 1H), 2.00-1.86 (m, 1H), 1.80 (s, 3H),1.68 (d, J=20.8 Hz, 3H). [α]²⁰ _(D)=−58° (c=0.1 g/100 mL, MeOH).

(3S,5R,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thionewas prepared in a similar way starting from(3S,5R,6R)-3,5-difluoro-6-(2-fluoro-5-nitrophenyl)-3,6-dimethylpiperidine-2-thione.

(3S,5S,6R)-6-(5-amino-2,3-difluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thionewas prepared in a similar way starting from(3S,5S,6R)-3,5-difluoro-6-(2,3-difluoro-5-nitrophenyl)-3,6-dimethylpiperidine-2-thione.

(3R,5S,6R)-6-(5-amino-2,3-difluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thionewas prepared in a similar way starting from(3R,5S,6R)-3,5-difluoro-6-(2,3-difluoro-5-nitrophenyl)-3,6-dimethylpiperidine-2-thione.

Intermediate: methyl-d₃-5-(methoxy-d₃)pyrazine-2-carboxylate

Sodium (0.094 g, 4.10 mmol) was added in small portions methanol-d₄(2.94 ml) and the reaction mixture was stirred until all sodium hasreacted. The solution was the added to another solution ofmethyl-5-chloropyrazine-2-carboxylate (0.6 g, 3.48 mmol) in methanol-d₄(0.98 ml). The reaction mixture was stirred for 1.5 hours at roomtemperature. The reaction mixture was concentrated in vacuo. 2 ml ofwater was added. The mixture was extracted with ethyl acetate. Theorganic phase was washed with brine, dried over MgSO₄ and concentratedin vacuo to give methyl-d₃-5-(methoxy-d₃)pyrazine-2-carboxylate.

Intermediate: 5-(methoxy-d₃)pyrazine-2-carboxylic acid

Methyl-d₃-5-(methoxy-d₃)pyrazine-2-carboxylate (424 mg, 2.43 mmol) wasdissolved in water (3 ml) and 1,4-dioxane (3 ml). Lithium hydroxide (146mg, 6.09 mmol) was added and the reaction mixture was stirred for 1hour. The reaction mixture was evaporated to about 2 ml and extractedwith diethylether. The organic phase was extracted with 1M NaOH and thecombined aqueous phases were acidified to pH 2 with 6N HCl (aq). Themixture was cooled on an icebath, and the solid compound collected togive 5-(methoxy-d₃)pyrazine-2-carboxylic acid.

Intermediate: methyl 5-(methoxy-d₃)picolinate

Methyl 5-hydroxypicolinate (2.88 g, 18.8 mmol) was dissolved indimethylformamide (108 ml) under argon. Potassium carbonate (7.20 g,52.1 mmol) was added and the orange suspension was stirred for 45minutes at room temperature. Iodomethane-d₃ (1.41 ml, 22.6 mmol) wasadded. The reaction mixture was stirred for 2 hours. Water was added.The mixture was extracted with ethyl acetate. The organic phase waswashed with brine, dried over MgSO₄ and concentrated in vacuo andpurified by column chromatography on silica gel (heptane:ethyl acetate)to give methyl 5-(methoxy-d₃)picolinate.

Intermediate: 5-(methoxy-d₃)picolinic acid

Methyl 5-(methoxy-d₃)picolinate (200 mg, 1.175 mmol) was dissolved inwater (1.5 ml) and 1,4-dioxane (3 ml). Lithium hydroxide (70.4 mg, 2.94mmol) was added and the reaction mixture was stirred for 1 hour. Thereaction mixture was evaporated to about 2 ml and extracted withdiethylether. The organic phase was extracted with 1M NaOH and thecombined aqueous phases were acidified to pH 2 with 6N HCl (aq). Themixture was cooled on an icebath and a precipitate was formed. Theprecipitate was collected to give 5-(methoxy-d₃)picolinic acid.

Preparation of the Compounds of the Invention Example 1N-(3-((2R,3S,5S)-6-Amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-fluoropicolinamide(compound 1)

To a solution 5-fluoropicolinic acid (0.019 g, 0.14 mmol) in DMF (1 mL),HATU (1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium3-oxide hexafluorophosphate) (0.046 g, 0.12 mmol) was added, thesolution was stirred 5 minutes. Then(3S,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thione(0.025 g, 0.092 mmol) and DIPEA (N,N-diisopropylethylamine) (0.08 mL,0.46 mmol) were added. The mixture was stirred at room temperature for 1hour. Saturated aqueous NH₄Cl was added and the mixture was extractedwith ethyl acetate. The organic phase was washed with brine, dried overMgSO₄, filtered and concentrated under reduced pressure. The residue wasdissolved in 7M ammonia in methanol (2 mL). The mixture was stirred at65° C. overnight, concentrated under reduce pressure and purified bycolumn chromatography on silica gel (heptane:ethyl acetate). Theobtained oil was dissolved in ethyl acetate and washed with saturatedaqueous NaHCO₃/water (1/1) five times. The organic phase wasconcentrated under reduced pressure to affordN-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-fluoropicolinamide(0.019 mmol, 21% yield). ¹H NMR (600 MHz, DMSO) δ 10.64 (s, 1H), 8.74(d, J=2.8 Hz, 1H), 8.23 (dd, J=8.7, 4.6 Hz, 1H), 7.98 (td, J=8.7, 2.9Hz, 1H), 7.89-7.75 (m, 2H), 7.16 (dd, J=11.8, 8.6 Hz, 1H), 6.11 (s, 2H),5.23-5.03 (m, 1H), 2.37-2.26 (m, 1H), 2.01-1.84 (m, 1H), 1.62 (d, J=23.9Hz, 3H), 1.52 (d, J=1.1 Hz, 3H).

LC-MS (m/z) 395.4 (MH⁺); t_(R)=0.47 minutes (Method B)

The following compounds were prepared in a way similar to example 1:

Example 2N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypyrazine-2-carboxamide(compound 2)

Prepared from(3S,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-methoxypyrazine-2-carboxylic acid.

¹H NMR (600 MHz, DMSO) δ 10.53 (s, 1H), 8.88 (d, J=1.3 Hz, 1H), 8.41 (d,J=1.3 Hz, 1H), 7.82 (m, 1H), 7.16 (dd, J=11.9, 8.7 Hz, 1H), 6.10 (broads, 2H), 5.18-5.07 (m, 1H), 4.03 (s, 3H), 2.37-2.26 (m, 1H), 1.99-1.83(m, 1H), 1.53 (d, J=23.9 Hz, 3H), 1.52 (s, 3H). LC-MS (m/z) 408.4 (MH⁺);t_(R)=0.47 minutes (Method B)

Example 3N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypicolinamide(compound 3)

Prepared from(3S,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-methoxypicolinic acid.

¹H NMR (600 MHz, DMSO) δ 10.46 (s, 1H), 8.43-8.34 (m, 1H), 8.16-8.06 (m,1H), 7.85 (ddd, J=8.7, 4.1, 2.8 Hz, 1H), 7.79 (dd, J=7.3, 2.8 Hz, 1H),7.61 (dd, J=8.7, 2.8 Hz, 1H), 7.15 (dd, J=11.9, 8.8 Hz, 1H), 6.46-5.73(m, 2H), 5.20-5.06 (m, 1H), 3.93 (s, 3H), 2.37-2.22 (m, 1H), 2.02-1.84(m, 1H), 1.62 (d, J=23.9 Hz, 3H), 1.52 (m, 3H). LC-MS (m/z) 407.4 (MH⁺);t_(R)=0.48 minutes (Method B)

Example 4N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-fluoropicolinamide(compound 4)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-fluoropicolinic acid.

¹H NMR (600 MHz, DMSO) δ 10.77 (s, 1H), 8.73 (d, J=2.8 Hz, 1H), 8.22(dd, J=8.7, 4.6 Hz, 1H), 7.97 (td, J=8.7, 2.8 Hz, 1H), 7.82-7.73 (m,1H), 7.71 (dd, J=7.2, 2.6 Hz, 1H), 7.17 (dd, J=11.7, 8.8 Hz, 1H), 6.25(s, 2H), 5.12 (dd, J=48.0, 2.5 Hz, 1H), 2.45-2.25 (m, 1H), 1.76-1.58 (m,1H), 1.56 (s, 3H), 1.53 (d, J=22.1 Hz, 3H). LC-MS (m/z) 395.1 (MH⁺);t_(R)=0.46 minutes (Method A)

Example 5N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypyrazine-2-carboxamide(compound 5)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-methoxypyrazine-2-carboxylic acid.

¹H NMR (600 MHz, DMSO) δ 10.67 (s, 1H), 8.67 (s, 1H), 8.41 (d, J=1.3 Hz,1H), 7.76 (m, 1H), 7.71 (dd, J=7.2, 2.6 Hz, 1H), 7.17 (dd, J=11.7, 8.8Hz, 1H), 6.30 (broad s, 2H), 5.12 (dd, J=47.9, 2.5 Hz, 1H), 4.02 (s,3H), 2.38-2.28 (m, 1H), 1.73-1.58 (m, 1H), 1.56 (s, 3H), 1.53 (d, J=22.1Hz, 3H). LC-MS (m/z) 408.2 (MH⁺); t_(R)=0.48 minutes (Method A)

Example 6N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-2-methyloxazole-4-carboxamide(compound 6)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 2-methyloxazole-4-carboxylic acid.

¹H NMR (600 MHz, DMSO) δ 10.37 (s, 1H), 8.65 (s, 1H), 7.78-7.72 (m, 1H),7.71-7.66 (m, 1H), 7.18 (dd, J=11.6, 8.9 Hz, 1H), 5.22-5.09 (m, 1H),2.50 (s, 3H), 2.43-2.33 (m, 1H), 1.75-1.62 (m, 1H), 1.60 (s, 3H), 1.56(d, J=22.1 Hz, 3H). LC-MS (m/z) 381.1 (MH⁺); t_(R)=0.43 minutes (MethodA)

Example 7N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypicolinamide(compound 7)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-methoxypicolinic acid.

¹H NMR (600 MHz, DMSO) δ 10.61 (s, 1H), 8.41-8.30 (m, 1H), 8.14-8.07 (m,1H), 7.80-7.74 (m, 1H), 7.71 (dd, J=7.3, 2.8 Hz, 1H), 7.60 (dd, J=8.8,2.8 Hz, 1H), 7.15 (dd, J=11.8, 8.8 Hz, 1H), 6.27 (s, 2H), 5.19-5.05 (m,1H), 3.93 (s, 3H), 2.45-2.27 (m, 1H), 1.76-1.59 (m, 1H), 1.56 (s, 3H),1.53 (d, J=22.1 Hz, 3H).

LC-MS (m/z) 407.1 (MH⁺); t_(R)=0.5 minutes (Method A)

Example 8N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)picolinamide(Compound 8)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-(methoxy-d₃)picolinic acid. ¹H NMR (600 MHz, DMSO) δ 10.72 (s,1H), 8.39 (d, J=2.8 Hz, 1H), 8.12 (d, J=8.7 Hz, 1H), 7.90 (s, 1H),7.80-7.75 (m, 1H), 7.60 (dd, J=8.7, 2.9 Hz, 1H), 7.21 (dd, J=11.6, 9.0Hz, 1H), 5.21 (d, J=47.5 Hz, 1H), 2.46-2.38 (m, 1H), 1.82-1.66 (m, 1H),1.64 (s, 3H), 1.61 (d, J=22.1 Hz, 3H). LC-MS (m/z) 410 (MH⁺); t_(R)=0.49(Method A)

Example 9N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-chloropicolinamide(Compound 9)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 4-chlorobenzoic acid. ¹H NMR (600 MHz, DMSO) δ 10.83 (s, 1H), 8.78(dd, J=2.4, 0.7 Hz, 1H), 8.18 (dd, J=8.4, 2.4 Hz, 1H), 8.15 (dd, J=8.4,0.7 Hz, 1H), 7.78 (ddd, J=8.7, 4.1, 2.8 Hz, 1H), 7.71 (dd, J=7.3, 2.7Hz, 1H), 7.17 (dd, J=11.7, 8.8 Hz, 1H), 6.21 (s, 2H), 5.11 (ddd, J=48.2,4.7, 2.1 Hz, 1H), 2.34 (dddd, J=20.7, 15.6, 8.9, 4.8 Hz, 1H), 1.72-1.57(m, 1H), 1.56 (s, 3H), 1.53 (d, J=22.1 Hz, 3H). LC-MS (m/z) 411.1 (MH⁺);t_(R)=0.53 (Method A)

Example 10N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-1-methyl-1H-imidazole-2-carboxamide(Compound 10)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 1-methyl-1H-imidazole-2-carboxylic acid. ¹H NMR (600 MHz, DMSO) δ10.53 (s, 1H), 7.72 (ddd, J=8.7, 4.2, 2.8 Hz, 1H), 7.61 (dd, J=7.3, 2.7Hz, 1H), 7.43 (d, J=0.7 Hz, 1H), 7.12 (dd, J=11.8, 8.8 Hz, 1H), 7.07 (d,J=1.0 Hz, 1H), 6.16 (s, 2H), 5.15-5.04 (m, 1H), 3.97 (s, 3H), 2.32(dddd, J=20.8, 15.5, 8.9, 4.9 Hz, 1H), 1.71-1.56 (m, 1H), 1.54 (s, 3H),1.51 (d, J=22.1 Hz, 3H). LC-MS (m/z) 380.1 (MH⁺); t_(R)=0.42 (Method A)

Example 11N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(trifluoromethyl)pyrazine-2-carboxamide(Compound 11)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-(trifluoromethyl)pyrazine-2-carboxylic acid. ¹H NMR (600 MHz,DMSO) δ 11.13 (s, 1H), 9.44 (d, J=1.0 Hz, 1H), 9.30 (d, J=1.0 Hz, 1H),7.81 (ddd, J=8.7, 4.1, 2.8 Hz, 1H), 7.74 (dd, J=7.2, 2.7 Hz, 1H), 7.20(dd, J=11.7, 8.8 Hz, 1H), 6.23 (s, 2H), 5.18-5.06 (m, 1H), 2.34 (dddd,J=20.7, 15.6, 9.0, 4.8 Hz, 1H), 1.71-1.58 (m, 1H), 1.56 (s, 3H), 1.53(d, J=22.0 Hz, 3H). LC-MS (m/z) 446.1 (MH⁺); t_(R)=0.53 (Method A)

Example 12N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-4-methylthiazole-2-carboxamide(Compound 12)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 4-methylthiazole-2-carboxylic acid. ¹H NMR (600 MHz, DMSO) δ 10.91(s, 1H), 7.78-7.72 (m, 1H), 7.71-7.67 (m, 2H), 7.16 (dd, J=11.7, 8.8 Hz,1H), 6.21 (s, 2H), 5.16-5.05 (m, 1H), 2.50 (t, J=2.0 Hz, 3H), 2.38-2.27(m, 1H), 1.70-1.56 (m, 1H), 1.55 (s, 3H), 1.52 (d, J=22.0 Hz, 3H). LC-MS(m/z) 397.1 (MH⁺); t_(R)=0.5 (Method A)

Example 13N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-2-(difluoromethyl)oxazole-4-carboxamide(Compound 13)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 1-(difluoromethyl)-1H-pyrazole-3-carboxylic acid. ¹H NMR (600 MHz,DMSO) δ 10.54 (s, 1H), 9.04 (s, 1H), 7.67 (ddd, J=8.7, 4.2, 2.8 Hz, 1H),7.62 (dd, J=7.2, 2.7 Hz, 1H), 7.33 (t, J=51.9 Hz, 1H), 7.15 (dd, J=11.7,8.8 Hz, 1H), 6.17 (s, 2H), 5.10 (ddd, J=48.2, 4.5, 2.1 Hz, 1H),2.38-2.27 (m, 1H), 1.69-1.56 (m, 1H), 1.55 (s, 3H), 1.51 (d, J=22.0 Hz,3H). LC-MS (m/z) 417.1 (MH⁺); t_(R)=0.47 (Method A)

Example 14N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-1-(difluoromethyl)-1H-pyrazole-3-carboxamide(Compound 14)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-(methoxy-d₃)pyrazine-2-carboxylic acid. ¹H NMR (600 MHz, DMSO) δ10.52 (s, 1H), 8.41 (d, J=2.7 Hz, 1H), 7.92 (t, J=58.7 Hz, 1H), 7.69(ddd, J=8.7, 4.1, 2.8 Hz, 1H), 7.63 (dd, J=7.3, 2.7 Hz, 1H), 7.15 (dd,J=11.8, 8.8 Hz, 1H), 7.01 (d, J=2.7 Hz, 1H), 6.19 (s, 2H), 5.11 (ddd,J=48.2, 4.5, 2.1 Hz, 1H), 2.39-2.26 (m, 1H), 1.73-1.56 (m, 1H), 1.55 (s,3H), 1.51 (d, J=22.0 Hz, 3H). LC-MS (m/z) 416.1 (MH⁺); t_(R)=0.46(Method A)

Example 15N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(difluoromethyl)pyrazine-2-carboxamide(Compound 15)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-cyano-3-methylpicolinic acid. ¹H NMR (600 MHz, DMSO) δ 11.06 (s,1H), 9.38 (d, J=1.4 Hz, 1H), 9.09 (d, J=0.9 Hz, 1H), 7.81 (ddd, J=8.7,4.1, 2.8 Hz, 1H), 7.74 (dd, J=7.2, 2.7 Hz, 1H), 7.26 (t, J=54.0 Hz, 1H),7.20 (dd, J=11.7, 8.8 Hz, 1H), 6.22 (s, 2H), 5.12 (ddd, J=48.2, 4.6, 2.1Hz, 1H), 2.41-2.28 (m, 1H), 1.72-1.58 (m, 1H), 1.56 (s, 3H), 1.53 (d,J=22.0 Hz, 3H). LC-MS (m/z) 428.1 (MH⁺); t_(R)=0.48 (Method A)

Example 16N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-4-chlorobenzamide(Compound 16)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-(methoxy-d₃)picolinic acid. ¹H NMR (600 MHz, DMSO) δ 10.45 (s,1H), 7.96-7.92 (m, 2H), 7.70 (ddd, J=8.7, 4.1, 2.8 Hz, 1H), 7.62-7.58(m, 2H), 7.54 (dt, J=7.2, 3.6 Hz, 1H), 7.16 (dd, J=11.8, 8.8 Hz, 1H),6.17 (s, 2H), 5.11 (ddd, J=48.2, 4.6, 2.1 Hz, 1H), 2.38-2.28 (m, 1H),1.71-1.57 (m, 1H), 1.56 (s, 3H), 1.50 (d, J=22.0 Hz, 3H). LC-MS (m/z)410.1 (MH⁺); t_(R)=0.54 (Method A)

Example 17N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-cyanopicolinamide(Compound 17)

Prepared from(3R,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-cyanopicolinic acid. ¹H NMR (600 MHz, DMSO) δ 10.99 (s, 1H), 9.19(dd, J=2.1, 0.9 Hz, 1H), 8.57 (dd, J=8.2, 2.1 Hz, 1H), 8.28 (dd, J=8.2,0.9 Hz, 1H), 7.79 (ddd, J=8.7, 4.1, 2.9 Hz, 1H), 7.72 (dd, J=7.2, 2.7Hz, 1H), 7.18 (dd, J=11.7, 8.8 Hz, 1H), 6.20 (s, 2H), 5.17-5.05 (m, 1H),2.41-2.26 (m, 1H), 1.69-1.56 (m, 1H), 1.55 (s, 3H), 1.52 (d, J=22.1 Hz,3H). LC-MS (m/z) 402.1 (MH⁺); t_(R)=0.47 (Method A)

Example 18N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4,5-difluorophenyl)-5-(methoxy-d₃)picolinamide(Compound 18)

Prepared from(3R,5S,6R)-6-(5-amino-2,3-difluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 2-(difluoromethyl)oxazole-4-carboxylic acid. ¹H NMR (600 MHz, DMSO)δ 10.89 (s, 1H), 8.38 (d, J=2.8 Hz, 1H), 8.12 (d, J=8.7 Hz, 1H),8.08-8.01 (m, 1H), 7.63-7.58 (m, 2H), 5.22-5.09 (m, 1H), 2.47-2.35 (m,1H), 1.85-1.69 (m, 1H), 1.62 (s, 3H), 1.58 (d, J=22.1 Hz, 3H). LC-MS(m/z) 428.1 (MH⁺); t_(R)=0.54 (Method A)

Example 19N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)picolinamide(Compound 19)

Prepared from(3S,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-(methoxy-d₃)picolinic acid. ¹H NMR (600 MHz, DMSO) δ 10.46 (s,1H), 8.39 (dd, J=2.9, 0.5 Hz, 1H), 8.12 (dd, J=8.7, 0.5 Hz, 1H),7.86-7.80 (m, 1H), 7.78 (dd, J=7.3, 2.7 Hz, 1H), 7.61 (dd, J=8.7, 2.9Hz, 1H), 7.15 (dd, J=11.8, 8.8 Hz, 1H), 6.07 (s, 2H), 5.12 (dd, J=48.5,6.1 Hz, 1H), 2.35-2.27 (m, 1H), 1.98-1.84 (m, 1H), 1.61 (d, J=23.9 Hz,3H), 1.51 (s, 3H). LC-MS (m/z) 410 (MH⁺); t_(R)=0.49 (Method A)

Example 20N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)pyrazine-2-carboxamide(Compound 20)

Prepared from(3S,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-(methoxy-d₃)picolinic acid. ¹H NMR (600 MHz, DMSO) δ 10.52 (s,1H), 8.88 (s, 1H), 8.40 (s, 1H), 7.86-7.78 (m, 2H), 7.16 (dd, J=11.6,8.9 Hz, 1H), 6.13 (s, 2H), 5.12 (dd, J=48.6, 5.3 Hz, 1H), 2.35-2.28 (m,1H), 2.01-1.84 (m, 1H), 1.62 (d, J=23.9 Hz, 3H), 1.52 (s, 3H). LC-MS(m/z) 411.2 (MH⁺); t_(R)=0.48 (Method A)

Example 21N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-cyano-3-methylpicolinamide(Compound 21)

Prepared from(3S,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-chloropicolinic acid. ¹H NMR (600 MHz, DMSO) δ 10.77 (s, 1H), 8.98(s, 1H), 8.39 (s, 1H), 7.89-7.82 (m, 1H), 7.64 (d, J=5.1 Hz, 1H), 7.17(dd, J=11.5, 9.1 Hz, 1H), 6.20 (s, 2H), 5.18-5.06 (m, 1H), 2.50 (s, 3H),2.37-2.28 (m, 1H), 1.97-1.83 (m, 1H), 1.62 (d, J=23.9 Hz, 3H), 1.52 (s,3H).

LC-MS (m/z) 416 (MH⁺); t_(R)=0.51 (Method B)

Example 22N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4,5-difluorophenyl)-5-(methoxy-d₃)picolinamide(Compound 22)

Prepared from(3S,5S,6R)-6-(5-amino-2,3-difluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-(difluoromethyl)pyrazine-2-carboxylic acid. ¹H NMR (600 MHz, DMSO)δ 10.68 (s, 1H), 8.39 (d, J=2.8 Hz, 1H), 8.12 (d, J=8.7 Hz, 1H),8.04-7.98 (m, 1H), 7.68 (d, J=5.1 Hz, 1H), 7.62 (dd, J=8.7, 2.9 Hz, 1H),6.36 (s, 2H), 5.10 (dd, J=48.6, 6.2 Hz, 1H), 2.38-2.29 (m, 1H),2.08-1.91 (m, 1H), 1.63 (d, J=23.7 Hz, 3H), 1.53 (s, 3H). LC-MS (m/z)428.2 (MH⁺); t_(R)=0.54 (Method A)

Example 23N-(3-((2R,3R,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)picolinamide(Compound 23)

Prepared from(3S,5R,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-(methoxy-d₃)picolinic acid. ¹H NMR (600 MHz, DMSO) δ 10.27 (s,1H), 8.39 (dd, J=2.9, 0.4 Hz, 1H), 8.14-8.11 (m, 1H), 8.08 (dd, J=7.3,2.8 Hz, 1H), 7.87-7.82 (m, 1H), 7.62 (dd, J=8.7, 2.9 Hz, 1H), 7.13 (dd,J=12.0, 8.8 Hz, 1H), 6.00 (s, 2H), 5.23-5.13 (m, 1H), 2.46-2.33 (m, 2H),1.62 (d, J=22.0 Hz, 3H), 1.36 (s, 3H). LC-MS (m/z) 410.1 (MH⁺);t_(R)=0.52 (Method B)

Example 24N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-bromopicolinamide(Compound 24)

Prepared from(3S,5S,6R)-6-(5-amino-2-fluoro-phenyl)-3,5-difluoro-3,6-dimethyl-piperidine-2-thioneand 5-bromopicolinic acid.

¹H NMR (600 MHz, DMSO) δ 10.70 (s, 1H), 8.86 (dd, J=2.3, 0.7 Hz, 1H),8.32 (dd, J=8.4, 2.3 Hz, 1H), 8.08 (dd, J=8.4, 0.6 Hz, 1H), 7.92-7.76(m, 2H), 7.17 (dd, J=11.8, 8.7 Hz, 1H), 6.17 (s, 2H), 5.19-5.07 (m, 1H),2.39-2.25 (m, 1H), 2.03-1.83 (m, 1H), 1.62 (d, J=23.9 Hz, 3H), 1.53 (s,3H).

LC-MS (m/z) 455.1 (MH⁺); t_(R)=0.54 (Method B)

Stereochemistry

Crystals were obtained by recrystallization of5-bromo-N-(3-((2R,3S,5S)-3,5-difluoro-2,5-dimethyl-6-thioxopiperidin-2-yl)-4-fluorophenyl)picolinamidefrom a mixture of heptane and ethyl acetate. The structure of5-bromo-N-(3-((2R,3S,5S)-3,5-difluoro-2,5-dimethyl-6-thioxopiperidin-2-yl)-4-fluorophenyl)picolinamide(FIG. 1) was elucidated by X-ray crystallography of said crystals. Thestructure shows the absolute and relative configuration of5-bromo-N-(3-((2R,3S,5S)-3,5-difluoro-2,5-dimethyl-6-thioxopiperidin-2-yl)-4-fluorophenyl)picolinamide.5-Bromo-N-(3-((2R,3S,5S)-3,5-difluoro-2,5-dimethyl-6-thioxopiperidin-2-yl)-4-fluorophenyl)picolinamidewas prepared as described in example 1 starting from(3S,5S,6R)-6-(5-amino-2-fluorophenyl)-3,5-difluoro-3,6-dimethylpiperidine-2-thioneand 5-bromopicolinic acid.

The absolute configurations of the exemplified compounds of the presentinvention can thus be rationalized.5-Bromo-N-(3-((2R,3S,5S)-3,5-difluoro-2,5-dimethyl-6-thioxopiperidin-2-yl)-4-fluorophenyl)picolinamidewas prepared from(3S,5S,6R)-6-(5-amino-2-fluorophenyl)-3,5-difluoro-3,6-dimethylpiperidine-2-thionewhich was prepared from XIIa (R4=tert-butoxy carbonyl) as shown inScheme 7, thus confirming the absolute configuration of XIIa. As aconsequence thereof, the absolute configuration of XIIb (R4=tert-butoxycarbonyl) is also confirmed.

Pharmacological TestingBACE1 Binding Assay

The binding assay was performed as SPA-based assay using a biotinylatedform of human BACE1 recombinantly expressed and subsequently purifiedfrom Freestyle HEK293 cells. The binding assay was run in a 50 mM sodiumacetate buffer, pH 4.5 containing 50 mM NaCl and 0.03% Tween-20 in whiteclear bottom 384 plates (Corning #3653). 10 nM (final concentration)radioligand([³H]—N-((1S,2R)-1-benzyl-3-cyclopropylamino-2-hydroxy-propyl)-5-(methanesulfonyl-methyl-amino)-N—((R)-1-phenyl-ethyl)-isophthalamide)(TRQ11569 purchased from GE Healthcare) was mixed with test compound ata given concentration, 6 nM (final concentration) human BACE1 and 25 μgStreptavidin coated PVT core SPA beads (RPNQ0007, GE Healthcare LifeSciences) in a total volume of 40 μl. Several concentrations of eachtest compound were tested in the assay for IC₅₀ determination. Theplates were incubated for one hour at room temperature and counted in aWallac Trilux counter. Total and non-specific binding were determinedusing buffer and 1 μM (final concentration) of the high affinity BACE1reference inhibitor(S)-6-[3-chloro-5-(5-prop-1-ynyl-pyridin-3-yl)-thiophen-2-yl]-2-imino-3,6-dimethyl-tetrahydro-pyrimidin-4-one,respectively. For each test compound, a IC₅₀ value (the concentrationmediating 50% inhibition of the specific binding of the radioligand) wasdetermined from concentration-response curve and used to calculate theK_(i) from the equation K_(i)=IC₅₀/(1+L/K_(d)), where L and K_(d) arethe final concentration of the radioligand used in the assay and thedissociation constant of the radioligand, respectively. The K_(d) of theradioligand was determined from saturation binding experiments.

TABLE 1 binding affinity of selected compounds Compound BACE1 No Ki (nM)1 30 2 26 3 23 4 98 5 51 6 58 7 39 8 58 9 36 10 820 11 190 12 99 13 6214 45 15 100 16 220 17 39 18 6.8 19 20 20 21 21 4.1 22 3.6 23 81 24 4.3BACE1 Efficacy Assay

The efficacy assay was performed as a FRET-based assay using acommercially available BACE1 kit (Life Technologies, P2985). 2 μl testcompound at 10 μM (final concentration) and 15 μl BACE1 enzyme from thekit (final concentration 3 nM) were preincubated for 15 minutes at roomtemperature before addition of 15 μl of substrate from the kit (250 nMfinal concentration) and incubated for additional 90 minutes at roomtemperature. The assay plate was subsequently read in a Pherastar(Ex540/Em590). The enzyme activity observed in presence of test compoundwere normalized to the enzyme activity observed in presence of bufferand 10 μM (final concentration) of the high affinity BACE1 referenceinhibitor(S)-6-[3-Chloro-5-(5-prop-1-ynyl-pyridin-3-yl)-thiophen-2-yl]-2-imino-3,6-dimethyl-tetra-hydropyrimidin-4-one,respectively. The efficacy of the test compounds was evaluated at 10 μM(final concentration) and defined as the percent inhibition of theenzyme activity using the equation % inhibition=100%−normalized enzymeactivity in percent.

TABLE 2 BACE1 activity of selected compounds Compound BACE1 inhibitionNo at 10 μM (%) 1 103 2 99 3 102 4 101 6 101 7 102 8 100 9 109 10 115 11104 12 118 13 108 14 112 15 108 16 103 18 101 19 106 20 106 21 117 22101 23 107 24 103Assessment of Aβ Levels in Rat Brain and Plasma Following BACE1Inhibition.Animals.

All rat care and experimental procedures were approved by LundbeckVeterinary Staff, according to Danish legislature. The rats weremaintained in a barrier facility with a 12/12-h light/dark cycle and adlibitum food and water access.

Treatment of Naïve Rats.

Young adult Male Sprague Dawley rats of approximately 250 g weight werepurchased from Charles River and received 0-30 mg/kg of vehicle (10% HPbetaCD+1M MeSO₄, pH 2.5) or test compounds (dissolved in vehicle) onlyby oral gavage (p.o). The compounds are dosed at a volume of 5 ml/kg.Cohorts of 5-10 animals were established for each treatment condition.

The animals undergoing treatment were closely monitored by veterinarystaff for any signs of toxicity. Monitoring parameters included bodyweight, physical appearance, changes in coat appearance, occurrence ofunprovoked behavior, and blunted or exaggerated responses to externalstimuli.

Tissue Collection.

At T=180 minutes after initial dosing the animals were stunned anddecapitated with a guillotine. Trunk-blood was sampled in EDTA coatedtubes after decapitation of the animal. The blood was centrifuged at2200G at 4° C. for 15 minutes and the plasma was collected and frozen at−80° C. The blood was aliquoted for Aβ ELISA and DMPK analysis.Immediately following sacrifice, the brain was extracted and split into2 halves. The right hemibrains were snap frozen on dry ice and stored at−80° C. The left half was dissected; with the front forebrain taken forAβ ELISA and the remainder used for DMPK analysis. These samples werealso snap frozen on dry ice and stored at −80° C. until use foranalysis.

Tissue Processing.

The cortex samples were thawed slightly on wet ice before they werehomogenized with a small volume dispersing instrument (T10 basicULTRA-TURRAX®) which was set at speed 5 for approximately 5-7 sec. Thetissue was processed in a 10 times volume of the weight, for example 100mg of tissue was homogenized in 1000 μL of Homogenization buffer.Homogenization buffer: 50 ml Milli Q water+50 nM NaCl+0.2% Diethylamin(DEA)+1 tablet of Complete Protease inhibitor cocktail+1 nM4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride irreversibleserine protease inhibitor (AEBSF).

After homogenization 450 μL aliquots of the samples are collected into a1.5 ml Eppendorf tube and placed on wet ice, 0.5% NP-40 (50 ul) wasadded to all samples and then they were incubated on ice for 30 min.After which all samples were sonicated using an Ultrasonic homogenizerwith 20 kHz homogeneous sound (SONOPLUS HD2070, Bandelin Electronic) 10pulse set at 12-13% power to extract all the Aβ species. The sampleswere then centrifuged (Ole Dich 157 MPRF Micro centrifuge) at 20000G for20 minutes at 4° C. After centrifugation 285 μL of the supernatant waspipetted into 600 μL microtubes tubes and neutralized with 15 μL of 1MTris-HCL buffer.

ELISA Protocol.

WAKO 294-62501 Human/Rat Abeta amyloid (40) kit was used for all ELISAanalyses. 30 μL plasma samples or 30 μL of the cortex supernatantsgenerated as described above were placed in 600 μL microtubes tubes onwet ice. To this 30 μL of 8M Urea (AppliChem A1049, 9025) are added togenerate a 2-fold dilution. Both plasma and cortex supernatants areincubated on ice for 30 min. Standard rows were prepared from thestandard peptide stock provided in the kit and standard diluentcontaining 1.6M Urea (200 μL 8M Urea+800 μL of standard diluent) and0.8M Urea (400 μL 8M Urea+3600 μL Standard diluent). A serial 2-folddilution of A340 from 100 μmol/ml to 0 μmol/L was prepared for theassay.

After incubation with urea, all samples were further diluted by additionof 5 times standard diluent from the Kit. This was done by adding 240 μLStandard Diluent to 60 μL sample/urea mixture, which was then mixedwell. 100 μL of each diluted sample was pipetted into designated wellsof the ELISA plate in duplicates. The plate was then covered andincubated overnight at 4° C. The following day, the ELISA kit wasbrought to room temperature before use. The incubated plate was washed 5times with the 20× washing solution diluted in Milli Q water. 100 μLHRP-conjugate was applied to each well, and the plate was covered andincubates at 4° C. for 1 hr. The wash was repeated again for 5 times.100 μL 3,3′,5,5′-Tetramethylbenzidine (TMB) solution was applied to eachwell and the plate was covered and incubated in the dark at roomtemperature for 30 minutes. 100 μL STOP-solution was next applied toeach well, and the plate was read at 450 nm wavelength in aspectrophotometer (Labsystems Multiscan Ascent) within 30 min of addingthe STOP-solution to the wells.

Concentration of Aβ in the samples was determined based on a standardcurve generated from standards containing known concentrations ofsynthetic Aβ40. Those skilled in the art will appreciate thatdiethylamine (DEA) and urea extractions will release soluble Aβ, andinsoluble Aβ respectively. Since the ELISA kit is validated and widelyused, it is accepted that as long as the treatment conditions and assayconditions are the same for each compound tested, then the assay shouldyield consistent robust data for the compounds tested and produceminimal discrepancies.

Data Analysis

To determine the concentration of Aβ40 in the samples, the interpolatedvalues of the samples loaded on plates are multiplied by 20 to accountfor the dilutions made when the volumes of DEA, urea and neutralizationsolution were added up. Values are calculated as percentage change inAβ40 compared to vehicle treated animals.

Compound 4 was administered at doses of 10 mg/kg p.o. and brain andplasma samples were collected at 3 hours post dose and the followingexposures were measured as described above.

Bioanalysis of Brain and Plasma Samples

TC was determined in plasma and brain homogenate using UltraPerformanceLC® (UPLC®) chromatography followed by tandem-MS (MS/MS) detection.

Apparatus:

Tecan Genesis RSP 200; Biomek NXP, Beckman Coulter; Sigma 4K15centrifuge; Acquity UPLC, Waters; Sciex API4000 TQ, Applied Biosystems;MS software: Analyst version 1.4.1

Chemicals

Acetonitrile, HPLC-grade, Fluka, No. 34967N; Methanol, HPLC-grade,Sigma-Aldrich, Lot 9003S; Formic acid, HPLC-grade, Riedel-de Haen, Lot51660; Purified water, Millipore Synergy UV

Sample Preparation

Brain homogenate was prepared by homogenizing the brain 1:4 (v/v) withwater:2-propanol:DMSO (50:30:20 v/v/v) followed by centrifugation andcollection of the supernatant. Calibration standards and QC samples wereprepared using a Hamilton robot. 150 μL of ISTD in acetonitrile (1 ng/mLISTD) was added to 25 μL of calibration standards, QC samples and testsamples (plasma and brain homogenate) using a Biomek robot. Aftercentrifugation (6200 g, 4° C., 20 min) 100 μL supernatant from eachsample was transferred to a new plate and mixed with 100 μL water with0.1% formic acid using a Biomek robot (method file InVivo transfer).After a quick centrifugation (6200 g, 4° C., 5 min) the samples wereplaced in the auto-sampler.

UPLC-MS/MS Analysis

MS/MS detection was done with an Applied Biosystems Sciex API 4000instrument in positive-ion electrospray ionisation mode. TC and ISTDwere detected at a parent>daughter mass to charge ratio (m/z). Nitrogenwas used for the nebulizer and collision gases. The peak area correlatedlinearly with the plasma and brain concentration of the analytes in therange of 1.00-1000 ng/mL plasma and 5.00-5000 ng/g brain (corrected fordilution). If the plasma/brain sample drug concentration was above 1000ng/mL or 5000 ng/g, the sample was diluted appropriately in blankplasma/blank brain homogenate before analysis.

Chromatographic System

Analytical Columns:

Waters Acquity UPLC HSS C18 SB (pH 2-8) 1.8 μm, 2.1×30 mm.

Mobile phase A: 0.1% aq. formic acid or 0.1% aq. ammonium hydroxide

Mobile phase B: Acetonitrile with 0.1% aq. formic acid or 0.1% aq.ammonium hydroxide.

Weak wash: Methanol

Strong wash: Acetonitrile/Isopropanol/formic acid (50/50/2 v/v/v)

Flow: 0.6 mL/min

Run time: 3 min.

To waste: 0-0.5 min

Temperature: 40° C.

Gradient:

Time (min) % A % B 0 98 2 0.01 98 2 1.5 5 95 2 5 95 2.2 98 2 3 98 2

TABLE 3 Results for compound 3 Dose Exp Brain/Plasma Aβ40 (mg/kg) (ng/g)ratio reduction (%) Brain Rat 10 671 1.4 35 Plasma Rat 489 24 Brain Rat30 1510 0.83 61 Plasma Rat 1826 53

TABLE 4 Results for compound 19 Dose Exp Brain/Plasma Aβ40 (mg/kg)(ng/g) ratio reduction (%) Brain Rat 10 1025 2.2 56 Plasma Rat 473 49Brain Rat 30 2772 2.3 66 Plasma Rat 1198 53

TABLE 5 Results for compound 20 Dose Exp Brain/Plasma Aβ40 (mg/kg)(ng/g) ratio reduction (%) Brain Rat 3 610 2.2 52 Plasma Rat 272 64

As shown in tables 3, 4 and 5 compounds of the present invention areable to penetrate the blood brain barrier and show efficacy in the CNS.

MDCK-MDR1 Assay

The permeability of the test compounds was assessed in MDCK-MDR1 cellsthat were cultured to confluency (4-6 days) in a 96 transwell plate.Test compounds were diluted with the transport buffer (HBSS+1% BSA) to aconcentration of 0.5 μM and applied to the apical or basolateral side ofthe cell monolayer. Permeation of the test compounds from A to Bdirection or B to A direction was determined in triplicate over a60-minute incubation time at 37° C. and 5% CO2 with a relative humidityof 95%. Test compounds were quantified by LC-MS/MS analysis based on thepeaks area ratios of analyte/IS in both the receiver and donor wells ofthe transwell plate.

The apparent permeability coefficient Papp (cm/s) was calculated usingthe equation:Papp=(dCr/dt)×Vr/(A×C0)

Where dCr/dt is the cumulative concentration of compound in the receiverchamber as a function of time (M/s); Vr is the solution volume in thereceiver chamber (0.05 mL on the apical side; 0.25 mL on the basolateralside); A is the surface area for the transport, i.e. 0.0804 cm² for thearea of the monolayer; C0 is the initial concentration in the donorchamber (VIM).

Compounds are classified Pgp substrates when efflux ratio (Papp BA/PappAB) is ≥2.

TABLE 5 BACE1 activity of selected compounds MDCK-MDR1 Compound effluxratio 1 1.09 2 0.79 3 0.96 4 1.17 5 1.53 6 1.1 7 5.67 8 0.95 9 1.31 1311.7 14 15.76 15 2.07 16 1.6 17 0.45 18 1.24 19 0.79 20 0.85 21 1.15 220.52 23 0.95

As shown in tables 5, the majority of the exemplified compounds of thepresent invention have MDCK-MDR1 efflux ratios below 2 and are thuslikely to be able to cross the blood brain barrier (E Kerns, L Di,Drug-like Properties: Concepts, Structure Design and Methods (2008)Elsevier).

The invention claimed is:
 1. A compound of formula I:

wherein: Ar is selected from the group consisting of phenyl, pyridyl,pyrimidyl, pyrazinyl, imidazolyl, pyrazolyl, thiazolyl, oxazolyl,isoxazolyl, and wherein Ar is optionally substituted with one or moresubstituent(s) selected from halogen, CN, C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, C₁-C₆ fluoroalkyl or C₁-C₆ alkoxy; and R¹ is one or morehydrogen, halogen, C₁-C₃ fluoroalkyl or C₁-C₃ alkyl; or apharmaceutically acceptable salt thereof.
 2. The compound orpharmaceutically acceptable salt thereof according to claim 1, whereinthe compound is of formula Ia or Ib:


3. The compound or pharmaceutically acceptable salt thereof according toclaim 1, wherein R¹ is F or H.
 4. The compound or pharmaceuticallyacceptable salt thereof according to claim 1, wherein Ar is optionallysubstituted with one or more F, Cl, Br, CN, C₁-C₃ alkyl, C₁-C₃fluoroalkyl or C₁-C₃ alkoxy.
 5. The compound or pharmaceuticallyacceptable salt thereof according to claim 1, wherein Ar is optionallysubstituted phenyl.
 6. The compound or pharmaceutically acceptable saltthereof of 1, wherein Ar is optionally substituted pyridyl.
 7. Thecompound or pharmaceutically acceptable salt thereof according to claim1, wherein Ar is optionally substituted pyrazinyl.
 8. The compound orpharmaceutically acceptable salt thereof according to claim 1, whereinAr is optionally substituted imidazolyl.
 9. The compound orpharmaceutically acceptable salt thereof according to claim 1, whereinAr is optionally substituted pyrazolyl.
 10. The compound orpharmaceutically acceptable salt thereof according to claim 1, whereinAr is optionally substituted oxazolyl.
 11. The compound orpharmaceutically acceptable salt thereof according to claim 1, whereinAr is optionally substituted thiazolyl.
 12. A compound selected from thegroup consisting of:N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-fluoropicolinamide,N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypyrazine-2-carboxamide,N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypicolinamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-fluoropicolinamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypyrazine-2-carboxamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-2-methyloxazole-4-carboxamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-methoxypicolinamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)picolinamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-chloropicolinamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-1-methyl-1H-imidazole-2-carboxamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(trifluoromethyl)pyrazine-2-carboxamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-4-methylthiazole-2-carboxamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-2-(difluoromethyl)oxazole-4-carboxamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-1-(difluoromethyl)-1H-pyrazole-3-carboxamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(difluoromethyl)pyrazine-2-carboxamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-4-chlorobenzamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-cyanopicolinamide,N-(3-((2R,3S,5R)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4,5-difluorophenyl)-5-(methoxy-d₃)picolinamide,N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)picolinamide,N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)pyrazine-2-carboxamide,N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-cyano-3-methylpicolinamide,N-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4,5-difluorophenyl)-5-(methoxy-d₃)picolinamide,N-(3-((2R,3R,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-(methoxy-d₃)picolinamide,andN-(3-((2R,3S,5S)-6-amino-3,5-difluoro-2,5-dimethyl-2,3,4,5-tetrahydropyridin-2-yl)-4-fluorophenyl)-5-bromopicolinamideor a pharmaceutically acceptable salt thereof.
 13. A pharmaceuticalcomposition comprising the compound or pharmaceutically acceptable saltthereof according to claim 1 and a pharmaceutically acceptable carrier.14. The pharmaceutical composition of claim 13, wherein said compound isof formula Ia or Ib:

or a pharmaceutically acceptable salt thereof.
 15. A pharmaceuticalcomposition comprising the compound or pharmaceutically acceptable saltthereof according to claim 12 and a pharmaceutically acceptable carrier.16. A method of treating a neurodegenerative or cognitive disorder ordisease, wherein said method comprises administering a therapeuticallyeffective amount of the compound, or pharmaceutically acceptable saltthereof, of claim 1 to a patient in need thereof, wherein saidneurodegenerative or cognitive disorder or disease is selected from thegroup consisting of familial Alzheimer's disease, sporadic Alzheimer'sdisease, preclinical Alzheimer's disease, prodromal Alzheimer's disease,mild cognitive impairment, Down's, syndrome, and cerebral amyloidangiopathy.
 17. The method of treating the neurodegenerative orcognitive disorder or disease of claim 16, wherein said compound is offormula Ia or Ib:

or a pharmaceutically acceptable salt thereof.
 18. A method of treatingthe neurodegenerative or cognitive disorder or disease, wherein saidmethod comprises administering a therapeutically effective amount of thecompound, or pharmaceutically acceptable salt thereof, of claim 12 to apatient in need thereof, wherein said neurodegenerative or cognitivedisorder or disease is selected from the group consisting of familialAlzheimer's disease, sporadic Alzheimer's disease, preclinicalAlzheimer's disease, prodromal Alzheimer's disease, mild cognitiveimpairment, Down's syndrome, and cerebral amyloid angiopathy.